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Determine rational functions from conditions

Learning goals

  • Uses zeros, holes and asymptotes to choose numerator and denominator factors.
  • Determines rational-function parameters from given points or graph features.
  • Constructs a rational function from a contextual relationship.
  • Checks a proposed rational rule against all supplied conditions.

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Determine rational functions from conditions 1
The graph of a rational function \(g\) is shown. It has the form \(g(x)=2+\frac{k}{x+1}\), where \(k\ne0\). a) Use the graph to read the x- and y-intercepts. b) Use the y-intercept from part a) to determine \(k\). Then verify the x-intercept algebraically. c) Explain why \(x=-1\) cannot be an x-intercept.
Figure for problem 512875

Hints

- Read the coordinates where the curve crosses each coordinate axis. - At the y-intercept, the input is \(0\); use that graph-read point in the given function form. - After finding \(k\), rewrite the function as one fraction before checking the x-intercept. - An x-intercept must be a point in the function's domain.

Solution

1. From the graph, the y-intercept is \((0,-6)\) and the x-intercept is \((3,0)\). 2. At the y-intercept, \(x=0\). Substitute \((0,-6)\) into the given form: \(-6=2+\frac{k}{1}\), so \(k=-8\). 3. Thus, \(g(x)=2-\frac{8}{x+1}=\frac{2x-6}{x+1}\). 4. For the x-intercept, set the numerator equal to zero: \(2x-6=0\), so \(x=3\). Since \(3+1\ne0\), the x-intercept is \((3,0)\), agreeing with the graph. 5. At \(x=-1\), the denominator is zero, so \(g\) is undefined there. Therefore, \(x=-1\) cannot be an x-intercept.

Answer

a) x-intercept: \((3,0)\); y-intercept: \((0,-6)\) b) \(k=-8\); the exact x-intercept is \((3,0)\) c) \(x=-1\) is excluded from the domain because the denominator is zero.
Determine rational functions from conditions 2
A rational function has the form \(f(x) = \frac{a}{x - h} + k\). Its vertical asymptote is \(x = 3\), its horizontal asymptote is \(y = 2\), and its graph passes through \(P(5, 3)\). Determine \(a\), \(h\), and \(k\), and write the function rule.

Hints

- The asymptotes determine \(h\) and \(k\) directly. - Substitute the given point after writing the function with an unknown \(a\). - Solve the resulting equation for \(a\).

Solution

1. The vertical asymptote \(x = 3\) gives \(h = 3\), and the horizontal asymptote \(y = 2\) gives \(k = 2\). 2. The function has the form \(f(x) = \frac{a}{x - 3} + 2\). 3. Substitute \(P(5, 3)\): \(3 = \frac{a}{5 - 3} + 2\). 4. This gives \(1 = \frac{a}{2}\), so \(a = 2\). 5. Therefore, \(f(x) = \frac{2}{x - 3} + 2\).

Answer

\(a = 2\), \(h = 3\), and \(k = 2\); \(f(x) = \frac{2}{x - 3} + 2\)
Determine rational functions from conditions 3
A rational function has the form \(g(x) = \frac{a}{x + d} + c\). Its vertical asymptote is \(x = -1\), its horizontal asymptote is \(y = 4\), and its graph crosses the \(y\)-axis at \((0, 1)\). Find \(a\) and write the complete function rule.

Hints

- Use the vertical asymptote to determine the denominator shift. - Use the horizontal asymptote to determine the vertical shift. - Substitute the given \(y\)-intercept to solve for \(a\).

Solution

1. The vertical asymptote \(x = -1\) means \(-d = -1\), so \(d = 1\). 2. The horizontal asymptote \(y = 4\) gives \(c = 4\). Therefore, \(g(x) = \frac{a}{x + 1} + 4\). 3. Substitute the \(y\)-intercept \((0, 1)\): \(1 = \frac{a}{0 + 1} + 4\). 4. Thus, \(1 = a + 4\), so \(a = -3\). 5. The complete function rule is \(g(x) = \frac{-3}{x + 1} + 4\).

Answer

\(a = -3\), and \(g(x) = \frac{-3}{x + 1} + 4\)
Determine rational functions from conditions 4
A rational function has the form \(h(x) = \frac{a}{x - h_0} + k\). Its vertical and horizontal asymptotes intersect at \((2, -1)\), and its graph has an \(x\)-intercept at \(x = 4\). Find the complete function rule.

Hints

- The coordinates of the asymptote intersection give the horizontal and vertical shifts. - An \(x\)-intercept has a function value of \(0\). - Substitute all known values into the general form to solve for the scale factor.

Solution

1. The asymptote intersection \((2, -1)\) gives \(h_0 = 2\) and \(k = -1\). Therefore, \(h(x) = \frac{a}{x - 2} - 1\). 2. The \(x\)-intercept at \(x = 4\) means that \((4, 0)\) lies on the graph. Substitute: \(0 = \frac{a}{4 - 2} - 1\). 3. Then \(1 = \frac{a}{2}\), so \(a = 2\). 4. Therefore, the function rule is \(h(x) = \frac{2}{x - 2} - 1\).

Answer

\(h(x) = \frac{2}{x - 2} - 1\)
Determine rational functions from conditions 5
The graph of \(f(x) = \frac{k}{x + 3} - 2\) passes through \(P(1, 1)\). Find \(k\).

Hints

- A point on the graph must satisfy the function equation. - Substitute the point's \(x\)-coordinate for \(x\) and its \(y\)-coordinate for \(f(x)\). - Isolate the parameter step by step.

Solution

1. Substitute the coordinates of \(P(1, 1)\): \(1 = \frac{k}{1 + 3} - 2\). 2. Then \(1 = \frac{k}{4} - 2\), so \(3 = \frac{k}{4}\). 3. Multiply by \(4\): \(k = 12\).

Answer

\(k = 12\)
Determine rational functions from conditions 6
A rational function has the form \(f(x)=\frac{a}{x-x_0}+y_0\). Its horizontal asymptote is \(y=4\), its vertical asymptote is \(x=-1\), and the point \(P=(1, 5)\) lies on its graph. Find \(a\), \(x_0\), and \(y_0\), and write the function rule.

Hints

- The horizontal translation and vertical translation determine the asymptotes. - Set the denominator equal to zero to locate the vertical asymptote. - Substitute the coordinates of the given point to find \(a\).

Solution

1. The horizontal asymptote \(y=4\) gives \(y_0=4\). 2. The vertical asymptote \(x=-1\) gives \(x_0=-1\). 3. Thus, \(f(x)=\frac{a}{x+1}+4\). Substitute \(P=(1, 5)\): \(5=\frac{a}{2}+4\). 4. Therefore, \(1=\frac{a}{2}\), so \(a=2\). The function is \(f(x)=\frac{2}{x+1}+4\).

Answer

\(a=2\), \(x_0=-1\), \(y_0=4\), and \(f(x)=\frac{2}{x+1}+4\)
Determine rational functions from conditions 7
Give one possible formula for a rational function \(f\) that satisfies both conditions. 1. The graph crosses the x-axis at \(x=5\). 2. The function has a vertical asymptote at \(x=-3\), with the same sign on both sides.

Hints

- An x-intercept comes from a numerator zero that is in the domain. - A vertical asymptote comes from a noncanceling denominator zero. - An even multiplicity produces the same sign on both sides of the asymptote. - Compare the behavior of \(\frac{1}{x}\) and \(\frac{1}{x^2}\).

Solution

1. An x-intercept at \(x=5\) requires the numerator factor \((x-5)\). 2. A vertical asymptote at \(x=-3\) without a sign change can be created by the even-power denominator factor \((x+3)^2\). 3. Therefore, one possible function is \(f(x)=\frac{x-5}{(x+3)^2}\).

Answer

One possible formula is \(f(x)=\frac{x-5}{(x+3)^2}\).
Determine rational functions from conditions 8
Find one rational function \(f\) whose domain is \(\mathbb{R}\setminus\{4\}\), whose horizontal asymptote is \(y=-2\), and whose graph has a vertical asymptote at \(x=4\) with a sign change across it.

Hints

- Use a denominator factor to exclude \(x=4\). - Use an odd multiplicity to create a sign change. - Match numerator and denominator degrees and leading coefficients to obtain \(y=-2\).

Solution

1. To exclude only \(x=4\) and create a sign-changing vertical asymptote, use the denominator factor \((x-4)\) to an odd power. Choose \(x-4\). 2. For horizontal asymptote \(y=-2\), use numerator and denominator polynomials of the same degree with leading-coefficient ratio \(-2\). 3. One example is \(f(x)=\frac{-2x}{x-4}\). At \(x=4\), the numerator equals \(-8\), so the factor does not cancel, and the vertical asymptote remains.

Answer

One possible formula is \(f(x)=\frac{-2x}{x-4}\).
Determine rational functions from conditions 9
Which function rule matches the translated hyperbola shown in the graph? a) \(f(x) = \frac{1}{x - 1} + 2\) b) \(f(x) = -\frac{1}{x - 1} + 2\) c) \(f(x) = -\frac{1}{x + 1} + 2\) d) \(f(x) = -\frac{1}{x - 1} - 2\)
Figure for problem 533147

Hints

- First identify the vertical and horizontal asymptotes. - Use the asymptotes to determine the horizontal and vertical translations. - Test a point with integer coordinates to determine the sign of the numerator. - Notice which two regions formed by the asymptotes contain the branches.

Solution

1. The graph approaches the vertical line \(x = 1\) and the horizontal line \(y = 2\). Therefore, the function has the form \(f(x) = \frac{a}{x - 1} + 2\). 2. The point \((0, 3)\) lies on the graph. Substitute it into the function rule: \(3 = \frac{a}{0 - 1} + 2\). 3. Solving gives \(3 = -a + 2\), so \(a = -1\). 4. Thus, \(f(x) = -\frac{1}{x - 1} + 2\), which is choice b).

Answer

b) \(f(x) = -\frac{1}{x - 1} + 2\)
Determine rational functions from conditions 10
The graph represents a function of the form \(f(x) = \frac{a}{x - h} + k\). Use the asymptotes to determine \(h\) and \(k\), and then use the marked point to find \(a\).
Figure for problem 533319

Hints

- The vertical asymptote gives \(h\). - The horizontal asymptote gives \(k\). - Substitute the marked point after finding \(h\) and \(k\).

Solution

1. The vertical asymptote is \(x = 2\), so \(h = 2\). 2. The horizontal asymptote is \(y = 1\), so \(k = 1\). The function has the form \(f(x) = \frac{a}{x - 2} + 1\). 3. The marked point is \((5, 2)\). Substitute it: \(2 = \frac{a}{5 - 2} + 1\). 4. This gives \(1 = \frac{a}{3}\), so \(a = 3\). 5. Therefore, \(f(x) = \frac{3}{x - 2} + 1\).

Answer

\(h = 2\), \(k = 1\), and \(a = 3\); \(f(x) = \frac{3}{x - 2} + 1\)
Determine rational functions from conditions 11
The graph represents a function of the form \(f(x) = \frac{a}{x - h} + k\). Determine \(a\), \(h\), and \(k\) from the graph.
Figure for problem 533320

Hints

- Use the vertical asymptote to find \(h\). - Use the horizontal asymptote to find \(k\). - Substitute the marked point to solve for \(a\).

Solution

1. The vertical asymptote is \(x = -3\), so \(h = -3\). 2. The horizontal asymptote is \(y = -1\), so \(k = -1\). The function has the form \(f(x) = \frac{a}{x + 3} - 1\). 3. The marked point is \((-1, -2)\). Substitute it: \(-2 = \frac{a}{-1 + 3} - 1\). 4. This gives \(-1 = \frac{a}{2}\), so \(a = -2\). 5. Therefore, \(f(x) = -\frac{2}{x + 3} - 1\).

Answer

\(a = -2\), \(h = -3\), and \(k = -1\); \(f(x) = -\frac{2}{x + 3} - 1\)
Determine rational functions from conditions 12
Use the graph to determine \(a\), \(h\), and \(k\) for \(f(x) = \frac{a}{x - h} + k\).
Figure for problem 533325

Hints

- The vertical asymptote gives the value of \(h\). - The horizontal asymptote gives the value of \(k\). - Substitute the marked point to determine \(a\).

Solution

1. The vertical asymptote is \(x = 3\), so \(h = 3\). 2. The horizontal asymptote is \(y = -4\), so \(k = -4\). The function has the form \(f(x) = \frac{a}{x - 3} - 4\). 3. The marked point is \((6, -2)\). Substitute it: \(-2 = \frac{a}{6 - 3} - 4\). 4. This gives \(2 = \frac{a}{3}\), so \(a = 6\). 5. Therefore, \(f(x) = \frac{6}{x - 3} - 4\).

Answer

\(a = 6\), \(h = 3\), and \(k = -4\); \(f(x) = \frac{6}{x - 3} - 4\)
Determine rational functions from conditions 13
Use the graph and marked point to find the rule in the form \(f(x)=\frac{a}{x}+c\). Explain how you found the values of \(a\) and \(c\).
Figure for problem 533326

Hints

- What horizontal value do the branches get closer to far from the origin? - How does that value appear in the function form? - Read the marked point and substitute its coordinates to find the missing coefficient.

Solution

1. The graph approaches the horizontal line \(y=2\), so \(c=2\) and \(f(x)=\frac{a}{x}+2\). The vertical asymptote is the y-axis, \(x=0\), consistent with the stated form. 2. Read the point \(P=(1,-1)\) from the graph. Substitution gives \(-1=\frac{a}{1}+2\), so \(a=-3\). 3. Therefore, \(f(x)=-\frac{3}{x}+2\).

Answer

\(a=-3\), \(c=2\); \(f(x)=-\frac{3}{x}+2\).
Determine rational functions from conditions 14
Determine the function rule for the hyperbola shown.
Figure for problem 533328

Hints

- Read the asymptotes carefully; each grid interval represents \(0.5\) unit. - Use the vertical asymptote to write the denominator. - Substitute the marked point to determine the numerator.

Solution

1. The vertical asymptote is \(x = -2.5\), and the horizontal asymptote is \(y = -0.5\). 2. Therefore, the function has the form \(f(x) = \frac{a}{x + 2.5} - 0.5\). 3. The marked point is \((-1.5, 0.5)\). Substitute it: \(0.5 = \frac{a}{-1.5 + 2.5} - 0.5\). 4. This gives \(1 = \frac{a}{1}\), so \(a = 1\). 5. Thus, \(f(x) = \frac{1}{x + 2.5} - 0.5\).

Answer

\(f(x) = \frac{1}{x + 2.5} - 0.5\)
Determine rational functions from conditions 15
The figure shows graphs p, q, and r from the family \(j_a(x)=\frac{a}{x^2+1}\). Find the value of \(a\) for each graph.
Figure for problem 534408

Hints

- Evaluate the function at \(x=0\). - Read the y-intercept of each graph. - For these functions, the y-intercept is also the extreme value.

Solution

1. At \(x=0\), \(j_a(0)=a\). Therefore, the y-intercept directly gives the parameter. 2. Graph p has y-intercept \(2\), so \(a=2\). Graph q has y-intercept \(4\), so \(a=4\). Graph r has y-intercept \(-1\), so \(a=-1\).

Answer

p) \(a=2\) q) \(a=4\) r) \(a=-1\)
Determine rational functions from conditions 16
The graph is a translated hyperbola. Determine a possible function rule for \(f\).
Figure for problem 534409

Hints

- Identify the horizontal line approached by the graph. - Determine where the graph has a vertical break. - Substitute a point with integer coordinates to find the numerator. - A vertical translation adds a constant outside the fraction.

Solution

1. The graph approaches the horizontal line \(y = 3\), so the function has the form \(f(x) = \frac{a}{x} + 3\). 2. The vertical asymptote is the y-axis, \(x = 0\), so no horizontal translation is needed. 3. The point \((1, 4)\) lies on the graph. Substitute it: \(4 = \frac{a}{1} + 3\). 4. Therefore, \(a = 1\), and \(f(x) = \frac{1}{x} + 3\).

Answer

One possible function rule is \(f(x) = \frac{1}{x} + 3\).
Determine rational functions from conditions 17
The graph represents a function of the form \(f(x) = \frac{a}{x - h} + k\). Determine \(h\), \(k\), and \(a\), and write the function rule.
Figure for problem 534411

Hints

- Use the vertical asymptote to find \(h\). - Use the horizontal asymptote to find \(k\). - Substitute a point on the graph to solve for \(a\).

Solution

1. The vertical asymptote is \(x = -1\), so \(h = -1\). 2. The horizontal asymptote is \(y = -2\), so \(k = -2\). Thus, \(f(x) = \frac{a}{x + 1} - 2\). 3. The graph crosses the y-axis at \((0, -1)\). Substitute this point: \(-1 = \frac{a}{0 + 1} - 2\). 4. Solving gives \(a = 1\). 5. Therefore, \(f(x) = \frac{1}{x + 1} - 2\).

Answer

\(h = -1\), \(k = -2\), and \(a = 1\); \(f(x) = \frac{1}{x + 1} - 2\)
Determine rational functions from conditions 18
Find one possible rule for the rational function shown. Also write its vertical and horizontal asymptotes.
Figure for problem 534412

Hints

- Read the two lines that the graph approaches. - Use these to fill in the unknown shifts in a translated reciprocal-function rule. - Choose a point with readable coordinates from the grid to determine the remaining coefficient.

Solution

1. The graph has vertical asymptote \(x=3\) and horizontal asymptote \(y=1\). 2. Use \(f(x)=\frac{a}{x-3}+1\). 3. The curve passes through \((4,3)\). Substituting gives \(3=\frac{a}{4-3}+1\), so \(a=2\). 4. Therefore, \(f(x)=\frac{2}{x-3}+1\).

Answer

Vertical asymptote: \(x=3\); horizontal asymptote: \(y=1\); \(f(x)=\frac{2}{x-3}+1\).
Determine rational functions from conditions 19
A function has the form \(p(x)=\frac{a}{x}+c\). Its graph has the horizontal asymptote \(y=-2\) and passes through \(A(4,-1)\). a) Find \(a\) and \(c\). b) Using your values from part a, let \(q(x)=\frac{-a}{x}+c\). Describe how the branches of \(q\) are positioned relative to those of \(p\) and their asymptotes. c) Find \(x\) when \(p(x)=-1.5\).

Hints

- What does the horizontal asymptote tell you about the constant term? - Substitute the known graph point to find the other coefficient. - Compare the signs of the two fractional terms for positive and negative inputs. - In the final equation, isolate the fraction before solving for the input.

Solution

1. The horizontal asymptote gives \(c=-2\). Substituting \(A(4,-1)\) gives \(-1=\frac{a}{4}-2\), so \(a=4\). 2. Hence \(p(x)=\frac{4}{x}-2\), while \(q(x)=-\frac{4}{x}-2\). Their common asymptotes are \(x=0\) and \(y=-2\). 3. Relative to the center \((0,-2)\), the branches of \(p\) lie above and right, and below and left. The branches of \(q\) lie above and left, and below and right. They are reflections across \(y=-2\). 4. Solve \(-1.5=\frac{4}{x}-2\): \(\frac{4}{x}=0.5\), so \(x=8\).

Answer

a) \(a=4\), \(c=-2\) b) The branches switch from upper-right/lower-left to upper-left/lower-right relative to \((0,-2)\); the graphs are reflected across \(y=-2\). c) \(x=8\)
Determine rational functions from conditions 20
The function \(h\) is defined by \(h(x) = \frac{k}{x - 4} - 3\). 1) Find \(k\), given that \(Q(6, 1)\) lies on the graph. 2) Using that value of \(k\), determine whether \(R(2, -5)\) lies above or below the graph of \(h\).

Hints

- If a point lies on a graph, its coordinates satisfy the function rule. - Rearrange the resulting equation to isolate \(k\). - Write the complete function rule before checking the second point. - Compare the point's \(y\)-coordinate with the function value at the same input.

Solution

1. Substitute \(Q(6, 1)\): \(1 = \frac{k}{6 - 4} - 3\). Then \(4 = \frac{k}{2}\), so \(k = 8\). 2. The function is \(h(x) = \frac{8}{x - 4} - 3\). 3. Evaluate at \(x = 2\): \(h(2) = \frac{8}{2 - 4} - 3 = -7\). 4. Since the point has \(y = -5\) and \(-5 > -7\), point \(R\) lies above the graph.

Answer

1) \(k = 8\) 2) Point \(R(2, -5)\) lies above the graph.
Determine rational functions from conditions 21
A rational function has the form \(f(x) = \frac{a}{x - h} + k\). Its vertical asymptote is \(x = 2\). The graph crosses the \(x\)-axis at \((4, 0)\) and the \(y\)-axis at \((0, -1)\). Find \(a\) and \(k\).

Hints

- Use the vertical asymptote to determine the horizontal shift \(h\). - Substitute each intercept into the function to create two equations. - Combine the equations to eliminate one variable.

Solution

1. The vertical asymptote \(x = 2\) gives \(h = 2\), so \(f(x) = \frac{a}{x - 2} + k\). 2. Substitute the \(x\)-intercept \((4, 0)\): \(0 = \frac{a}{4 - 2} + k\), so \(\frac{a}{2} + k = 0\). 3. Substitute the \(y\)-intercept \((0, -1)\): \(-1 = \frac{a}{0 - 2} + k\), so \(-\frac{a}{2} + k = -1\). 4. Add the two equations: \(2k = -1\), so \(k = -\frac{1}{2}\). 5. Substitute \(k = -\frac{1}{2}\) into \(\frac{a}{2} + k = 0\): \(\frac{a}{2} - \frac{1}{2} = 0\), so \(a = 1\).

Answer

\(a = 1\) and \(k = -\frac{1}{2}\)
Determine rational functions from conditions 22
A rational function has the form \(f(x)=\frac{a}{x-h}+k\). Its vertical asymptote is \(x=-2\), its horizontal asymptote is \(y=1\), and it passes through \(P(0,2)\). a) Find \(h\), \(k\), and \(a\). b) Write the complete function rule. c) Describe how the graph would change if \(a\) were \(-2\) instead of its value from part a).

Hints

- How are the horizontal and vertical shifts related to the asymptotes? - Substitute the known graph point into the partially filled function rule. - Compare the output's signed distance from the horizontal asymptote before and after the sign change.

Solution

1. The asymptotes give \(h=-2\) and \(k=1\), so \(f(x)=\frac{a}{x+2}+1\). 2. Substitute \(P(0,2)\): \(2=\frac{a}{2}+1\), giving \(a=2\). 3. Thus \(f(x)=\frac{2}{x+2}+1\). Replacing \(a=2\) with \(a=-2\) reverses the sign of the fractional term, reflecting the graph across its horizontal asymptote \(y=1\).

Answer

a) \(h=-2\), \(k=1\), \(a=2\) b) \(f(x)=\frac{2}{x+2}+1\) c) The graph is reflected across \(y=1\).
Determine rational functions from conditions 23
A rational function has the form \(f(x) = \frac{a}{x + 1} + c\). Its graph crosses the \(y\)-axis at \((0, 3)\) and the \(x\)-axis at \((2, 0)\). Find \(a\) and \(c\), and write the complete function rule.

Hints

- Substitute the coordinates of each intercept into the general function rule. - The two substitutions create a system of two equations. - Eliminate one variable or express one variable in terms of the other.

Solution

1. Substitute the \(y\)-intercept \((0, 3)\): \(3 = \frac{a}{0 + 1} + c\), so \(a + c = 3\). 2. Substitute the \(x\)-intercept \((2, 0)\): \(0 = \frac{a}{2 + 1} + c\), so \(\frac{a}{3} + c = 0\). 3. Subtract the second equation from the first: \(a - \frac{a}{3} = 3\). Thus, \(\frac{2a}{3} = 3\), so \(a = 4.5\). 4. Substitute \(a = 4.5\) into \(\frac{a}{3} + c = 0\): \(1.5 + c = 0\), so \(c = -1.5\). 5. Therefore, the function rule is \(f(x) = \frac{4.5}{x + 1} - 1.5\).

Answer

\(a = 4.5\), \(c = -1.5\), and \(f(x) = \frac{4.5}{x + 1} - 1.5\)
Determine rational functions from conditions 24
The graph of \(g(x) = \frac{k}{x + 2} - 4\) passes through \(P(2, -1)\). a) Find the value of \(k\). b) Find the \(x\)-intercept and the \(y\)-intercept of \(g\).

Hints

- A point on the graph must satisfy the function equation. - Substitute the coordinates of \(P\) first to determine \(k\). - After finding \(k\), use \(x = 0\) for the \(y\)-intercept and \(g(x) = 0\) for the \(x\)-intercept.

Solution

1. Because \(P(2, -1)\) lies on the graph, substitute \(x = 2\) and \(g(x) = -1\): \(-1 = \frac{k}{2 + 2} - 4\). 2. Then \(3 = \frac{k}{4}\), so \(k = 12\). 3. The function is \(g(x) = \frac{12}{x + 2} - 4\). For the \(y\)-intercept, substitute \(x = 0\): \(g(0) = \frac{12}{2} - 4 = 2\). Therefore, the \(y\)-intercept is \((0, 2)\). 4. For the \(x\)-intercept, set \(g(x) = 0\): \(0 = \frac{12}{x + 2} - 4\). Then \(4 = \frac{12}{x + 2}\), so \(4(x + 2) = 12\). Thus, \(x = 1\). 5. Therefore, the \(x\)-intercept is \((1, 0)\).

Answer

a) \(k = 12\) b) The \(x\)-intercept is \((1, 0)\), and the \(y\)-intercept is \((0, 2)\).
Determine rational functions from conditions 25
A rational function has the form \(f(x) = \frac{a}{x - 4} + 2\), where \(a\) is a real number. a) Find the value of \(a\) that makes the graph pass through the origin \((0, 0)\). b) For this value of \(a\), determine whether the graph has any other intercepts. Justify your answer algebraically.

Hints

- Passing through the origin means that \(f(0) = 0\). - Use the known point to solve for the parameter. - After finding \(a\), solve for all \(x\)-intercepts and remember that every \(y\)-intercept has \(x = 0\).

Solution

1. Because the graph passes through \((0, 0)\), substitute \(x = 0\) and \(f(x) = 0\): \(0 = \frac{a}{0 - 4} + 2\). 2. Then \(0 = -\frac{a}{4} + 2\), so \(\frac{a}{4} = 2\) and \(a = 8\). 3. With \(a = 8\), the function is \(f(x) = \frac{8}{x - 4} + 2\). Its \(y\)-intercept is determined by the single input \(x = 0\), which already gives \((0, 0)\). 4. To check for another \(x\)-intercept, solve \(0 = \frac{8}{x - 4} + 2\). Then \(-2 = \frac{8}{x - 4}\), so \(x - 4 = -4\) and \(x = 0\). 5. Therefore, the origin is the only intercept of the graph.

Answer

a) \(a = 8\) b) No. The only \(x\)-intercept is \((0, 0)\), and \(x = 0\) can produce only one \(y\)-intercept, so there are no additional intercepts.
Determine rational functions from conditions 26
Consider the family of functions \(g_k(x) = \frac{k}{x - 2} + 3\), where \(k \neq 0\). a) Find the value of \(k\) that makes the graph cross the \(x\)-axis at \(x = 5\). b) For the value of \(k\) found in part a), find the \(y\)-intercept.

Hints

- At an \(x\)-intercept, the function value is \(0\). - Substitute the known input and output to solve for \(k\). - To find the \(y\)-intercept, substitute \(x = 0\).

Solution

1. An \(x\)-intercept at \(x = 5\) means that \((5, 0)\) lies on the graph. Substitute \(x = 5\) and \(g_k(x) = 0\): \(0 = \frac{k}{5 - 2} + 3\). 2. Then \(0 = \frac{k}{3} + 3\), so \(-3 = \frac{k}{3}\) and \(k = -9\). 3. The function is \(g(x) = \frac{-9}{x - 2} + 3\). For the \(y\)-intercept, substitute \(x = 0\): \(g(0) = \frac{-9}{0 - 2} + 3 = 4.5 + 3 = 7.5\). 4. Therefore, the \(y\)-intercept is \((0, 7.5)\).

Answer

a) \(k = -9\) b) The \(y\)-intercept is \((0, 7.5)\).
Determine rational functions from conditions 27
Consider the function \(g(x) = \frac{8}{x - d} + 2\). Its graph crosses the \(y\)-axis at \((0, -2)\). a) Find the value of \(d\). b) Find the \(x\)-intercept of the graph.

Hints

- At every point on the \(y\)-axis, the input is \(0\). - Use the known intercept to solve for the parameter before finding the other intercept. - At an \(x\)-intercept, the function value is \(0\).

Solution

1. Substitute the \(y\)-intercept \((0, -2)\): \(-2 = \frac{8}{0 - d} + 2\). 2. Then \(-4 = \frac{8}{-d}\). Multiplying by \(-d\) gives \(4d = 8\), so \(d = 2\). 3. The function is \(g(x) = \frac{8}{x - 2} + 2\). To find the \(x\)-intercept, set \(g(x) = 0\): \(0 = \frac{8}{x - 2} + 2\). 4. Then \(-2 = \frac{8}{x - 2}\), so \(-2(x - 2) = 8\). Thus, \(-2x + 4 = 8\), giving \(x = -2\). 5. Therefore, the \(x\)-intercept is \((-2, 0)\).

Answer

a) \(d = 2\) b) The \(x\)-intercept is \((-2, 0)\).
Determine rational functions from conditions 28
The graph of \(g(x) = \frac{k}{x + 4} - 2\) crosses the \(y\)-axis at \((0, 1)\). a) Find the value of \(k\). b) Find the \(x\)-intercept of the graph.

Hints

- Substitute the coordinates of the known intercept to find the parameter. - At an \(x\)-intercept, the function value is \(0\). - Determine \(k\) before beginning part b).

Solution

1. Substitute the \(y\)-intercept \((0, 1)\): \(1 = \frac{k}{0 + 4} - 2\). 2. Then \(3 = \frac{k}{4}\), so \(k = 12\). 3. The function is \(g(x) = \frac{12}{x + 4} - 2\). To find the \(x\)-intercept, set \(g(x) = 0\): \(0 = \frac{12}{x + 4} - 2\). 4. Then \(2 = \frac{12}{x + 4}\), so \(2(x + 4) = 12\). Thus, \(x + 4 = 6\) and \(x = 2\). 5. Therefore, the \(x\)-intercept is \((2, 0)\).

Answer

a) \(k = 12\) b) The \(x\)-intercept is \((2, 0)\).
Determine rational functions from conditions 29
Consider the functions \(f(x) = \frac{4}{x - 2} + 2\) and \(g(x) = \frac{a}{x - 2} + 4\). a) Find the \(x\)-intercept of \(f\). b) Find the value of \(a\) that makes \(g\) have the same \(x\)-intercept as \(f\).

Hints

- First find the input where \(f(x) = 0\). - Having the same \(x\)-intercept means that \(g\) must also equal \(0\) at that input. - Substitute the intercept into \(g\) and solve for \(a\).

Solution

1. Set \(f(x) = 0\): \(0 = \frac{4}{x - 2} + 2\). 2. Then \(-2 = \frac{4}{x - 2}\), so \(-2(x - 2) = 4\). Thus, \(x - 2 = -2\) and \(x = 0\). The \(x\)-intercept of \(f\) is \((0, 0)\). 3. For \(g\) to have the same \(x\)-intercept, \(g(0) = 0\). Substitute: \(0 = \frac{a}{0 - 2} + 4\). 4. Then \(0 = -\frac{a}{2} + 4\), so \(\frac{a}{2} = 4\) and \(a = 8\).

Answer

a) The \(x\)-intercept of \(f\) is \((0, 0)\). b) \(a = 8\)
Determine rational functions from conditions 30
The graph of \(h(x) = \frac{24}{x + a} - 4\) crosses the \(y\)-axis at \((0, 2)\). a) Find the value of \(a\). b) Find the \(x\)-intercept. c) Explain mathematically why no point on the graph has a \(y\)-coordinate of \(-4\).

Hints

- Substitute the coordinates of the given \(y\)-intercept to find \(a\). - Set the function equal to \(0\) to find the \(x\)-intercept. - In part c), consider when a fraction can equal \(0\).

Solution

1. Substitute the \(y\)-intercept \((0, 2)\): \(2 = \frac{24}{0 + a} - 4\). 2. Then \(6 = \frac{24}{a}\), so \(a = 4\). 3. The function is \(h(x) = \frac{24}{x + 4} - 4\). To find the \(x\)-intercept, set \(h(x) = 0\): \(0 = \frac{24}{x + 4} - 4\). 4. Then \(4 = \frac{24}{x + 4}\), so \(4(x + 4) = 24\). Thus, \(x = 2\), and the \(x\)-intercept is \((2, 0)\). 5. To test whether \(h(x) = -4\), write \(-4 = \frac{24}{x + 4} - 4\). This simplifies to \(0 = \frac{24}{x + 4}\). 6. A fraction with a nonzero numerator cannot equal \(0\), so the equation has no solution. Therefore, the graph never reaches \(y = -4\).

Answer

a) \(a = 4\) b) The \(x\)-intercept is \((2, 0)\). c) Setting \(h(x) = -4\) gives \(\frac{24}{x + 4} = 0\), which has no solution because the numerator is nonzero.
Determine rational functions from conditions 31
Consider \(h_1(x) = \frac{4}{x - 2} + 1\) and \(h_2(x) = \frac{k}{x + 1}\). a) Find the \(y\)-intercept of \(h_1\). b) Find the value of \(k\) that makes \(h_2\) have the same \(y\)-intercept as \(h_1\). c) For the value of \(k\) found in part b), determine which function has no \(x\)-intercept. Justify your answer.

Hints

- First evaluate the first function at \(x = 0\). - Equal \(y\)-intercepts mean equal function values at \(x = 0\). - A rational expression can equal \(0\) only when its numerator is \(0\).

Solution

1. Substitute \(x = 0\) into \(h_1\): \(h_1(0) = \frac{4}{0 - 2} + 1 = -1\). Therefore, the \(y\)-intercept is \((0, -1)\). 2. For \(h_2\) to have the same \(y\)-intercept, require \(h_2(0) = -1\). Since \(h_2(0) = \frac{k}{1} = k\), it follows that \(k = -1\). 3. For \(h_1\), solve \(0 = \frac{4}{x - 2} + 1\). Then \(-1 = \frac{4}{x - 2}\), so \(x - 2 = -4\) and \(x = -2\). Thus, \(h_1\) has the \(x\)-intercept \((-2, 0)\). 4. For \(h_2(x) = \frac{-1}{x + 1}\), the numerator is the nonzero constant \(-1\). Therefore, the function can never equal \(0\), so \(h_2\) has no \(x\)-intercept.

Answer

a) The \(y\)-intercept of \(h_1\) is \((0, -1)\). b) \(k = -1\) c) \(h_2\) has no \(x\)-intercept because \(\frac{-1}{x + 1}\) cannot equal \(0\).
Determine rational functions from conditions 32
The graph of \(g(x) = \frac{a}{x + 3} + 4\) crosses the \(x\)-axis at \(x = -4\). a) Find the value of \(a\). b) Find the \(y\)-intercept.

Hints

- At an \(x\)-intercept, the output is \(0\). - Use the given intercept to solve for the parameter. - After finding \(a\), substitute \(x = 0\).

Solution

1. The \(x\)-intercept at \(x = -4\) means \(g(-4) = 0\). Substitute: \(0 = \frac{a}{-4 + 3} + 4\). 2. Then \(0 = -a + 4\), so \(a = 4\). 3. The function is \(g(x) = \frac{4}{x + 3} + 4\). Substitute \(x = 0\): \(g(0) = \frac{4}{3} + 4 = \frac{16}{3}\). 4. Therefore, the \(y\)-intercept is \(\left(0, \frac{16}{3}\right)\).

Answer

a) \(a = 4\) b) The \(y\)-intercept is \(\left(0, \frac{16}{3}\right)\).
Determine rational functions from conditions 33
Consider \(g(x)=\frac{a}{x-2}+3\) and \(h(x)=\frac{-a}{x-2}+3\), where \(a\ne0\). a) Describe how the two graphs are related. b) Find \(a\) so that the graph of \(g\) passes through \(Q(1,1)\). c) For this value of \(a\), determine algebraically whether \(Q(1,1)\) also lies on the graph of \(h\).

Hints

- Compare the two formulas relative to their common horizontal asymptote. - For the same allowed \(x\), how do the vertical displacements from \(y=3\) compare? - Substitute the coordinates of \(Q\) into \(g\), then test the same input in \(h\).

Solution

1. Both graphs have vertical asymptote \(x=2\) and horizontal asymptote \(y=3\). Changing \(a\) to \(-a\) places corresponding points the same distance on opposite sides of \(y=3\), so the graphs are reflections across \(y=3\). 2. Substitute \(Q(1,1)\) into \(g\): \(1=\frac{a}{1-2}+3\). Then \(1=-a+3\), so \(a=2\). 3. With \(a=2\), \(h(x)=\frac{-2}{x-2}+3\). Evaluate \(h(1)=\frac{-2}{-1}+3=5\). 4. Since \(h(1)=5\ne1\), \(Q(1,1)\) does not lie on the graph of \(h\).

Answer

a) The graphs are reflections of each other across \(y=3\). b) \(a=2\) c) No. Since \(h(1)=5\), \(Q(1,1)\) is not on the graph of \(h\).
Determine rational functions from conditions 34
The graph of \(g(x) = \frac{a}{x - 2} + 4\) passes through the \(y\)-intercept \((0, 3)\). Find \(a\), and then find the \(x\)-intercept of the graph.

Hints

- Substitute the given \(y\)-intercept to find \(a\). - Write the complete function rule before finding the next intercept. - At an \(x\)-intercept, the function value is \(0\).

Solution

1. Substitute \((0, 3)\): \(3 = \frac{a}{0 - 2} + 4\). 2. Then \(-1 = -\frac{a}{2}\), so \(a = 2\). The function is \(g(x) = \frac{2}{x - 2} + 4\). 3. Set \(g(x) = 0\): \(0 = \frac{2}{x - 2} + 4\). Then \(-4 = \frac{2}{x - 2}\), so \(-4(x - 2) = 2\). 4. Thus, \(-4x + 8 = 2\), so \(-4x = -6\) and \(x = 1.5\). 5. Therefore, the \(x\)-intercept is \((1.5, 0)\).

Answer

\(a = 2\), and the \(x\)-intercept is \((1.5, 0)\).
Determine rational functions from conditions 35
A function has the form \(h(x) = \frac{a}{x} + c\), and its graph passes through \(A(2, 4)\) and \(B(4, 3)\). Find \(a\) and \(c\), and write the complete function rule.

Hints

- Two unknown parameters require two independent equations. - Substitute each point into the general function rule. - Subtract the equations to eliminate one parameter.

Solution

1. Substitute \(A(2, 4)\): \(4 = \frac{a}{2} + c\). 2. Substitute \(B(4, 3)\): \(3 = \frac{a}{4} + c\). 3. Subtract the second equation from the first: \(1 = \frac{a}{2} - \frac{a}{4} = \frac{a}{4}\). Therefore, \(a = 4\). 4. Substitute \(a = 4\) into \(4 = \frac{a}{2} + c\): \(4 = 2 + c\), so \(c = 2\). 5. The function rule is \(h(x) = \frac{4}{x} + 2\).

Answer

\(a = 4\), \(c = 2\), and \(h(x) = \frac{4}{x} + 2\)
Determine rational functions from conditions 36
A function has the form \(f(x) = \frac{a}{x + 4} - 2\), and its graph passes through \(P(0, 1.5)\). a) Find \(a\). b) Find the \(x\)-intercept of the graph.

Hints

- A point on the graph must satisfy the function equation. - Use the given point to determine the unknown parameter. - After finding the complete function rule, set the function equal to \(0\).

Solution

1. Substitute \(P(0, 1.5)\): \(1.5 = \frac{a}{0 + 4} - 2\). 2. Then \(3.5 = \frac{a}{4}\), so \(a = 14\). 3. The function is \(f(x) = \frac{14}{x + 4} - 2\). Set \(f(x) = 0\): \(0 = \frac{14}{x + 4} - 2\). 4. Then \(2 = \frac{14}{x + 4}\), so \(2(x + 4) = 14\). Thus, \(x + 4 = 7\) and \(x = 3\). 5. Therefore, the \(x\)-intercept is \((3, 0)\).

Answer

a) \(a = 14\) b) The \(x\)-intercept is \((3, 0)\).
Determine rational functions from conditions 37
Consider the family \(f(x) = \frac{6}{x} + q\). a) Find the \(x\)-intercept when \(q = -2\). b) Find \(q\) so that the graph passes through \(P(3, 4)\). c) Find the value of \(q\) for which the graph has no \(x\)-intercept. Justify your answer.

Hints

- At an \(x\)-intercept, the output is \(0\). - Substitute both coordinates of the given point. - Compare what happens when \(q = 0\) with what happens when \(q \neq 0\). - A rational expression with a nonzero constant numerator cannot equal \(0\).

Solution

1. When \(q = -2\), solve \(0 = \frac{6}{x} - 2\). Then \(2 = \frac{6}{x}\), so \(x = 3\). The \(x\)-intercept is \((3, 0)\). 2. For the graph to pass through \(P(3, 4)\), substitute \(x = 3\) and \(f(x) = 4\): \(4 = \frac{6}{3} + q\). Thus, \(4 = 2 + q\), so \(q = 2\). 3. An \(x\)-intercept requires \(0 = \frac{6}{x} + q\). If \(q \neq 0\), then \(x = -\frac{6}{q}\), so there is an \(x\)-intercept. 4. If \(q = 0\), the equation becomes \(0 = \frac{6}{x}\), which has no solution because the numerator is nonzero. Therefore, \(q = 0\) is the only value for which the graph has no \(x\)-intercept.

Answer

a) The \(x\)-intercept is \((3, 0)\). b) \(q = 2\) c) \(q = 0\), because \(\frac{6}{x}\) can never equal \(0\).
Determine rational functions from conditions 38
Consider the family \(f_k(x)=k-\frac{8}{x}\), where \(x\ne0\). a) Find \(k\) so that the graph passes through \(A(4,1)\). b) How many x-intercepts does the graph have? Analyze the cases \(k=0\) and \(k\ne0\). c) Iva claims, “For some value of \(k\), \(f_k\) is a linear function.” Evaluate the claim mathematically.

Hints

- A rational expression with a nonzero constant numerator cannot equal \(0\). - Compare the cases \(k=0\) and \(k\ne0\) separately. - A linear function cannot contain the variable in a denominator.

Solution

1. Substitute \(A(4,1)\): \(1=k-\frac{8}{4}=k-2\). Therefore, \(k=3\). 2. An x-intercept satisfies \(0=k-\frac{8}{x}\). 3. If \(k\ne0\), then \(\frac{8}{x}=k\), so \(x=\frac{8}{k}\). Therefore, there is exactly one x-intercept. 4. If \(k=0\), then the equation is \(0=-\frac{8}{x}\), which has no solution because the numerator is nonzero. Therefore, there is no x-intercept. 5. Iva's claim is false. Changing \(k\) only changes the vertical shift. The term \(-\frac{8}{x}\) remains for every \(k\), so the function is never linear.

Answer

a) \(k=3\) b) If \(k\ne0\), there is exactly one x-intercept at \(x=\frac{8}{k}\). If \(k=0\), there is no x-intercept. c) The claim is false. The nonzero term \(-\frac{8}{x}\) remains for every value of \(k\), so the function is never linear.
Determine rational functions from conditions 39
Find one rational function \(g\) that satisfies both conditions. 1. Its domain is \(\mathbb{R}\setminus\{3, 5\}\). 2. Its only zero is \(x=-2\). Give a possible formula for \(g(x)\), and briefly justify your choice.

Hints

- Use denominator factors to create the excluded domain values. - Use a numerator factor to create the required zero. - Make sure no numerator factor cancels a denominator factor. - More than one correct function may be possible.

Solution

1. To exclude exactly \(x=3\) and \(x=5\), choose the denominator \((x-3)(x-5)\). 2. To create exactly one zero at \(x=-2\), choose the numerator \(x+2\). 3. No factor cancels, and \(-2\) is in the domain. Therefore, one possible function is \(g(x)=\frac{x+2}{(x-3)(x-5)}\).

Answer

One possible formula is \(g(x)=\frac{x+2}{(x-3)(x-5)}\). The denominator excludes \(3\) and \(5\), and the numerator has its only zero at \(-2\).
Determine rational functions from conditions 40
Give one possible formula for a rational function \(f\) that satisfies all three conditions. - Its graph has a hole at \(x=1\). - It has a vertical asymptote at \(x=-2\), with opposite signs on the two sides. - Its horizontal asymptote is \(y=2\).

Hints

- A hole can be created with a common numerator and denominator factor. - A noncanceling denominator factor creates a vertical asymptote. - Use the degrees and leading coefficients to control the horizontal asymptote. - Use an odd multiplicity at the vertical asymptote to produce a sign change.

Solution

1. A hole at \(x=1\) requires a common factor \((x-1)\) in the numerator and denominator. 2. A vertical asymptote with a sign change at \(x=-2\) can be created by including the factor \((x+2)\) to the first power in the denominator and not in the numerator. 3. To obtain the horizontal asymptote \(y=2\), use numerator and denominator polynomials of the same degree with leading-coefficient ratio \(2\). 4. One example is \(f(x)=\frac{2x(x-1)}{(x-1)(x+2)}\). It has the required hole, vertical asymptote, and horizontal asymptote.

Answer

One possible formula is \(f(x)=\frac{2x(x-1)}{(x-1)(x+2)}\).
Determine rational functions from conditions 41
Find one rational function \(f(x)=\frac{p(x)}{q(x)}\), where both \(p\) and \(q\) have degree \(2\), that satisfies all three conditions. - It has a double zero at \(x=-1\). - Its domain is all real numbers. - Its graph has y-intercept \(P=(0, 2)\).

Hints

- Represent a double zero with a squared numerator factor. - Choose a quadratic denominator that is always positive. - Use the y-intercept to determine the scale factor. - More than one correct function may be possible.

Solution

1. A double zero at \(x=-1\) requires \(p(x)=a(x+1)^2\). 2. For the domain to be all real numbers, choose a quadratic denominator with no real zeros, such as \(q(x)=x^2+1\). 3. The y-intercept condition gives \(2=f(0)=\frac{a(0+1)^2}{0^2+1}=a\), so \(a=2\). 4. Therefore, one possible function is \(f(x)=\frac{2(x+1)^2}{x^2+1}\).

Answer

One possible formula is \(f(x)=\frac{2(x+1)^2}{x^2+1}\).
Determine rational functions from conditions 42
For each part, give one possible formula for a rational function \(f\) with the stated features. a) The graph has an x-intercept at \(x=4\) and a vertical asymptote at \(x=-1\). b) The domain is \(\mathbb{R}\setminus\{-2, 2\}\), and the function has a zero at \(x=0\). c) The graph has no x-intercepts and has a vertical asymptote at \(x=5\), with the same sign on both sides.

Hints

- Numerator zeros produce x-intercepts when the denominator is nonzero. - Denominator zeros determine excluded domain values. - An even power in the denominator produces the same sign on both sides of a vertical asymptote. - A nonzero constant numerator has no zeros.

Solution

1. For part a, place \((x-4)\) in the numerator and \((x+1)\) in the denominator. One example is \(f(x)=\frac{x-4}{x+1}\). 2. For part b, use denominator factors \((x-2)(x+2)\) and numerator factor \(x\). One example is \(f(x)=\frac{x}{(x-2)(x+2)}=\frac{x}{x^2-4}\). 3. For part c, use a nonzero constant numerator so there are no zeros. A squared denominator factor creates a vertical asymptote without a sign change. One example is \(f(x)=\frac{1}{(x-5)^2}\).

Answer

a) \(f(x)=\frac{x-4}{x+1}\) b) \(f(x)=\frac{x}{x^2-4}\) c) \(f(x)=\frac{1}{(x-5)^2}\)
Determine rational functions from conditions 43
Find one possible rational function \(g\) for each set of conditions. a) The zeros are \(x=3\) and \(x=-3\), and the horizontal asymptote is \(y=2\). b) The function is undefined at \(x=1\), has no zeros, and passes through \(P=(0, 4)\). c) The graph is tangent to the x-axis at \(x=2\), and the y-axis is a vertical asymptote.

Hints

- Use numerator factors to create the required zeros and their multiplicities. - Use denominator factors to create excluded values and vertical asymptotes. - Use the ratio of leading coefficients to control a horizontal asymptote. - Substitute a given point to determine an unknown scale factor.

Solution

1. For part a, use numerator factors \((x-3)(x+3)\). To obtain horizontal asymptote \(y=2\), choose a denominator of the same degree with no common factors and make the leading-coefficient ratio \(2\). One example is \(g(x)=\frac{2(x^2-9)}{x^2+1}\). 2. For part b, a nonzero constant numerator gives no zeros, and the factor \((x-1)\) creates the excluded value. Let \(g(x)=\frac{c}{x-1}\). Since \(g(0)=4\), \(4=\frac{c}{-1}\), so \(c=-4\). Thus, \(g(x)=\frac{-4}{x-1}\). 3. For part c, tangency to the x-axis at \(x=2\) requires a double zero, so use \((x-2)^2\) in the numerator. The y-axis is \(x=0\), so place \(x\) in the denominator. One example is \(g(x)=\frac{(x-2)^2}{x}\).

Answer

a) \(g(x)=\frac{2(x^2-9)}{x^2+1}\) b) \(g(x)=\frac{-4}{x-1}\) c) \(g(x)=\frac{(x-2)^2}{x}\)
Determine rational functions from conditions 44
Find a rational function \(f(x)=\frac{p(x)}{q(x)}\) such that \(f(x)\to-\infty\) as \(x\to\infty\) and the line \(x=5\) is a vertical asymptote.

Hints

- Choose the degrees and leading coefficients so the function decreases without bound. - Use a denominator factor to create the vertical asymptote. - It may help to begin with a polynomial plus a proper rational expression. - Check that the numerator is not zero at the vertical asymptote.

Solution

1. To make \(f(x)\to-\infty\), choose a rational function whose polynomial part has a negative leading term. Start with \(f(x)=-x+\frac{1}{x-5}\). 2. The denominator factor \((x-5)\) creates a vertical asymptote at \(x=5\), and the numerator of the fraction is nonzero there. 3. Write the expression as one rational function: \(f(x)=\frac{-x(x-5)+1}{x-5}=\frac{-x^2+5x+1}{x-5}\). 4. As \(x\to\infty\), the term \(-x\) dominates, so \(f(x)\to-\infty\). At \(x=5\), the numerator equals \(1\), so the vertical asymptote is not canceled.

Answer

One possible function is \(f(x)=\frac{-x^2+5x+1}{x-5}\).
Determine rational functions from conditions 45
Find one rational function \(f(x)=\frac{p(x)}{q(x)}\) with all three features. - Its horizontal asymptote is \(y=1.5\). - Its vertical asymptotes are \(x=-1\) and \(x=2\). - Its graph passes through the origin.

Hints

- Use the vertical asymptotes to construct the denominator. - Use equal numerator and denominator degrees for a nonzero horizontal asymptote. - Passing through the origin requires \(f(0)=0\). - Check that no denominator factor cancels.

Solution

1. To create vertical asymptotes at \(x=-1\) and \(x=2\), choose \(q(x)=(x+1)(x-2)=x^2-x-2\). 2. For horizontal asymptote \(y=1.5\), use a quadratic numerator with leading coefficient \(1.5\). 3. Passing through the origin requires the numerator to equal zero at \(x=0\). Choose \(p(x)=1.5x^2\). 4. Therefore, one possible function is \(f(x)=\frac{1.5x^2}{x^2-x-2}\). The numerator is nonzero at \(x=-1\) and \(x=2\), so both vertical asymptotes remain.

Answer

One possible formula is \(f(x)=\frac{1.5x^2}{x^2-x-2}\).
Determine rational functions from conditions 46
Find one rational function \(f\) with all three properties. 1. It has a zero at \(x=3\). 2. It has a vertical asymptote at \(x=-1\), with the same sign on both sides. 3. As \(x\) approaches \(-1\) from either side, \(f(x)\) falls without bound.

Hints

- Use a numerator factor to create the zero. - Use an even-power denominator factor to avoid a sign change at the asymptote. - Check the signs of the numerator and denominator near \(x=-1\).

Solution

1. A zero at \(x=3\) requires the numerator factor \((x-3)\). 2. A vertical asymptote at \(x=-1\) without a sign change can be produced by the squared denominator factor \((x+1)^2\). 3. For \(f(x)=\frac{x-3}{(x+1)^2}\), the denominator approaches \(0\) through positive values as \(x\) approaches \(-1\) from either side, while the numerator approaches \(-4\). Therefore, the function falls without bound on both sides, so all conditions are satisfied.

Answer

One possible formula is \(f(x)=\frac{x-3}{(x+1)^2}\).
Determine rational functions from conditions 47
Find one rational function \(h\) whose domain is \(\mathbb{R}\setminus\{0\}\), whose horizontal asymptote is \(y=1\), and whose graph has a vertical asymptote at \(x=0\) with the same sign on both sides. The graph must also pass through \(P=(2, 2)\).

Hints

- Use an even power in the denominator to avoid a sign change at the vertical asymptote. - Write the function as the horizontal-asymptote value plus a rational term that approaches zero. - Substitute the given point to determine the remaining parameter. - Check that the numerator is nonzero at \(x=0\).

Solution

1. A vertical asymptote at \(x=0\) without a sign change can be created with the denominator \(x^2\). 2. To build in the horizontal asymptote \(y=1\), use \(h(x)=1+\frac{a}{x^2}\). 3. Substitute \(P=(2, 2)\): \(2=1+\frac{a}{2^2}\). Thus, \(1=\frac{a}{4}\), so \(a=4\). 4. Therefore, \(h(x)=1+\frac{4}{x^2}=\frac{x^2+4}{x^2}\).

Answer

One possible formula is \(h(x)=\frac{x^2+4}{x^2}\).
Determine rational functions from conditions 48
Find one possible formula for a rational function \(f\) whose graph has all three features. - A vertical asymptote at \(x=3\) - A horizontal asymptote at \(y=-1\) - A y-intercept at \(S_y=(0, 2)\)

Hints

- Use the vertical asymptote to choose a denominator factor. - Use the ratio of leading coefficients to obtain the horizontal asymptote. - Substitute \(x=0\) to use the y-intercept. - Check that no factor cancels at \(x=3\).

Solution

1. Use the form \(f(x)=\frac{ax+b}{x-3}\), which has a possible vertical asymptote at \(x=3\). 2. The horizontal asymptote is the ratio of leading coefficients, so \(a=-1\). 3. The y-intercept condition gives \(2=f(0)=\frac{b}{-3}\), so \(b=-6\). 4. Therefore, one possible function is \(f(x)=\frac{-x-6}{x-3}\). The numerator is nonzero at \(x=3\), so the vertical asymptote remains.

Answer

One possible formula is \(f(x)=\frac{-x-6}{x-3}\).
Determine rational functions from conditions 49
Find one possible formula for a rational function \(h\) whose graph has all four features. 1. A vertical asymptote at \(x=4\) 2. A hole at \(x=1\) 3. A horizontal asymptote at \(y=2\) 4. The point \(P=(0, 1)\) lies on the graph.

Hints

- A vertical asymptote comes from a noncanceling denominator factor. - A hole comes from a common numerator and denominator factor. - Use the leading-coefficient ratio for the horizontal asymptote. - Substitute the given point to determine the remaining factor.

Solution

1. Use the denominator factors \((x-4)(x-1)\). The factor \((x-4)\) creates the vertical asymptote, while \((x-1)\) will create a hole. 2. Include \((x-1)\) in the numerator so it cancels algebraically but remains excluded from the original domain. 3. To obtain horizontal asymptote \(y=2\), use a quadratic numerator with leading coefficient twice that of the denominator. Let \(h(x)=\frac{2(x-r)(x-1)}{(x-4)(x-1)}\). 4. Substitute \(P=(0, 1)\): \(1=\frac{2(0-r)(-1)}{(-4)(-1)}=\frac{r}{2}\), so \(r=2\). 5. Therefore, one possible function is \(h(x)=\frac{2(x-2)(x-1)}{(x-4)(x-1)}\).

Answer

One possible formula is \(h(x)=\frac{2(x-2)(x-1)}{(x-4)(x-1)}\).
Determine rational functions from conditions 50
Find one possible formula for a rational function \(h\) whose graph has all four features. 1. It is symmetric about the y-axis. 2. Its vertical asymptotes are \(x=-3\) and \(x=3\). 3. Its horizontal asymptote is \(y=-1\). 4. It is tangent to the x-axis at the origin.

Hints

- An even function is symmetric about the y-axis. - Use denominator factors for the two vertical asymptotes. - Tangency at an x-intercept requires an even-multiplicity zero. - Use the leading-coefficient ratio for the horizontal asymptote.

Solution

1. Symmetry about the y-axis suggests an even function containing only even powers of \(x\). 2. The vertical asymptotes suggest the denominator \((x-3)(x+3)=x^2-9\). 3. Tangency to the x-axis at the origin requires a zero of even multiplicity, so use the numerator factor \(x^2\). 4. To obtain horizontal asymptote \(y=-1\), the ratio of leading coefficients must be \(-1\). Therefore, choose numerator \(-x^2\). 5. One possible function is \(h(x)=\frac{-x^2}{x^2-9}\).

Answer

One possible formula is \(h(x)=\frac{-x^2}{x^2-9}\).
Determine rational functions from conditions 51
An open-top cylindrical water tank must have volume \(2\,\text{m}^3\). a) Write the tank height \(h(r)\) as a function of the base radius \(r\), where \(h\) and \(r\) are measured in meters. b) The base material costs \(\$30\) per square meter, and the side material costs \(\$20\) per square meter. Write the total material cost \(K(r)\) as a function of \(r\). c) Analyze \(K(r)\) as \(r\to0^+\) and as \(r\to\infty\). Explain both results in context.

Hints

- Use \(V=\pi r^2h\) for the cylinder volume. - The open tank consists of one circular base and one lateral surface. - Identify which term of the cost function dominates at each end of the domain.

Solution

1. The volume equation is \(\pi r^2h=2\). Therefore, \(h(r)=\frac{2}{\pi r^2}\) for \(r>0\). 2. The base costs \(30\pi r^2\). The lateral area is \(2\pi rh\), so the side costs \(20(2\pi rh)=40\pi rh\). Substitute \(h(r)\): \(K(r)=30\pi r^2+40\pi r\left(\frac{2}{\pi r^2}\right)=30\pi r^2+\frac{80}{r}\). 3. As \(r\to0^+\), \(\frac{80}{r}\to\infty\), so \(K(r)\to\infty\). A very narrow tank must be extremely tall, making the side area very large. 4. As \(r\to\infty\), \(30\pi r^2\to\infty\), so \(K(r)\to\infty\). A very wide tank requires an extremely large base.

Answer

a) \(h(r)=\frac{2}{\pi r^2}\), \(r>0\) b) \(K(r)=30\pi r^2+\frac{80}{r}\), \(r>0\) c) \(K(r)\to\infty\) as \(r\to0^+\) and as \(r\to\infty\). The side cost dominates for very small \(r\), and the base cost dominates for very large \(r\).
Determine rational functions from conditions 52
A translated reciprocal graph has center of symmetry \(Z=(4, 3)\) and passes through \(P=(2, 5.5)\). a) Find its equation in the form \(h(x)=\frac{k}{x-x_0}+c\). b) Rewrite the function as one fraction in the form \(h(x)=\frac{Ax+B}{Cx+D}\). c) Find the x-intercept and y-intercept.

Hints

- The center coordinates determine the vertical and horizontal asymptotes. - Substitute the given point to find \(k\). - Combine the terms using a common denominator. - Set \(x=0\) for the y-intercept and set the numerator equal to zero for the x-intercept.

Solution

1. The center \(Z=(4, 3)\) gives the asymptotes \(x=4\) and \(y=3\). Therefore, \(h(x)=\frac{k}{x-4}+3\). 2. Substitute \(P=(2, 5.5)\): \(5.5=\frac{k}{2-4}+3\). Thus, \(2.5=\frac{k}{-2}\), so \(k=-5\). 3. Therefore, \(h(x)=\frac{-5}{x-4}+3=\frac{-5+3(x-4)}{x-4}=\frac{3x-17}{x-4}\). 4. For the y-intercept, \(h(0)=\frac{-17}{-4}=\frac{17}{4}=4.25\), giving \((0, 4.25)\). 5. For the x-intercept, solve \(3x-17=0\). Thus, \(x=\frac{17}{3}\), giving \(\left(\frac{17}{3}, 0\right)\).

Answer

a) \(h(x)=\frac{-5}{x-4}+3\) b) \(h(x)=\frac{3x-17}{x-4}\) c) x-intercept: \(\left(\frac{17}{3}, 0\right)\); y-intercept: \((0, 4.25)\)
Determine rational functions from conditions 53
A cargo plane flies \(600\) miles to a destination and then immediately returns. The wind speed is constant at \(40\,\text{mph}\). Let \(x\), in miles per hour, be the plane's airspeed in still air. For \(x>40\), the total travel time is \(T(x)=\frac{600}{x+40}+\frac{600}{x-40}\) hours. a) Show that \(T(x)=\frac{1200x}{x^2-1600}\). b) Find the total travel time when the airspeed is \(160\,\text{mph}\) and when it is \(200\,\text{mph}\). Express each result in hours and minutes. c) Find the vertical and horizontal asymptotes relevant to the domain \(x>40\). d) Explain why the model cannot be used for \(0<x<40\).

Hints

- Add the two fractions using a common denominator. - Convert a decimal part of an hour to minutes by multiplying by \(60\). - Identify where a denominator approaches \(0\), and compare degrees for the end behavior. - Interpret the sign of the ground speed \(x-40\).

Solution

1. Use the common denominator \((x+40)(x-40)=x^2-1600\): \(T(x)=\frac{600(x-40)+600(x+40)}{x^2-1600}=\frac{1200x}{x^2-1600}\). 2. \(T(160)=\frac{1200\cdot160}{160^2-1600}=8\), so the trip takes \(8\) hours. 3. \(T(200)=\frac{1200\cdot200}{200^2-1600}=6.25\), so the trip takes \(6\) hours \(15\) minutes. 4. In the relevant domain, the vertical asymptote is \(x=40\). Since the denominator has greater degree than the numerator, the horizontal asymptote is \(y=0\). 5. If \(0<x<40\), then the plane's ground speed into the wind, \(x-40\), is negative. The plane cannot reach the destination against the wind, so the travel-time expression is not physically meaningful.

Answer

a) \(T(x)=\frac{1200x}{x^2-1600}\) b) At \(160\,\text{mph}\): \(8\) hours; at \(200\,\text{mph}\): \(6\) hours \(15\) minutes c) Vertical asymptote: \(x=40\); horizontal asymptote: \(y=0\) d) The headwind exceeds the plane's airspeed, so the plane cannot make forward progress on one leg.
Determine rational functions from conditions 54
Find one possible rational function \(f\) with all four features. - It has a zero at \(x=-3\). - It has a vertical asymptote at \(x=2\), with a sign change across it. - It has a vertical asymptote at \(x=-1\), with the same sign on both sides. - Its horizontal asymptote is the x-axis.

Hints

- Use a numerator factor for the zero. - Use an odd denominator multiplicity for a sign-changing vertical asymptote. - Use an even denominator multiplicity for no sign change. - Make the numerator degree smaller than the denominator degree to obtain horizontal asymptote \(y=0\).

Solution

1. Use the numerator factor \((x+3)\) to create the zero at \(x=-3\). 2. Use the first-power denominator factor \((x-2)\) to create a sign-changing vertical asymptote at \(x=2\). 3. Use the squared denominator factor \((x+1)^2\) to create a vertical asymptote without a sign change at \(x=-1\). 4. The numerator has degree \(1\), and the denominator has degree \(3\), so the horizontal asymptote is \(y=0\). 5. One possible function is \(f(x)=\frac{x+3}{(x-2)(x+1)^2}\).

Answer

One possible formula is \(f(x)=\frac{x+3}{(x-2)(x+1)^2}\).
Determine rational functions from conditions 55
Consider \(f(x) = \frac{1}{x}\) and \(g(x) = \frac{a}{x}\). a) The graph of \(g\) passes through \(P(0.5, 8)\). Find \(a\). b) Describe how the graph of \(g\) is obtained from the graph of \(f\). c) If \(a\) were negative, in which quadrants would the branches of \(g\) lie? Justify your answer using signs.

Hints

- A point on the graph must satisfy the function equation. - Compare \(g(x)\) with \(f(x)\) after finding \(a\). - Determine the sign of the quotient when the numerator and denominator have opposite signs.

Solution

1. Substitute \(P(0.5, 8)\): \(8 = \frac{a}{0.5}\). Multiplying by \(0.5\) gives \(a = 4\). 2. Therefore, \(g(x) = \frac{4}{x} = 4f(x)\). The graph of \(g\) is a vertical stretch of the graph of \(f\) by a factor of \(4\). 3. If \(a < 0\), then \(x\) and \(g(x)\) have opposite signs. Positive inputs give negative outputs, placing one branch in Quadrant IV; negative inputs give positive outputs, placing the other branch in Quadrant II.

Answer

a) \(a = 4\) b) The graph of \(g\) is a vertical stretch of the graph of \(f\) by a factor of \(4\). c) For \(a < 0\), the branches lie in Quadrants II and IV because the input and output have opposite signs.
Determine rational functions from conditions 56
The graph shows a translated hyperbola with function rule \(f(x) = \frac{a}{x - d} + c\). a) Read the equations of the vertical and horizontal asymptotes from the graph. b) Find \(c\) and \(d\). c) Use a point with exact coordinates on the graph to find \(a\). Then write the complete function rule.
Figure for problem 532162

Hints

- Which lines does the graph approach without reaching? - Which input makes the denominator \(0\), and how does that determine \(d\)? - What remains of the function as \(|x|\) becomes very large? - Substitute a clearly readable point to find \(a\).

Solution

1. The graph approaches the vertical line \(x = -2\) and the horizontal line \(y = 1\), so these are the asymptotes. 2. Since the vertical asymptote is \(x = d\), \(d = -2\). Since the horizontal asymptote is \(y = c\), \(c = 1\). 3. The function has the form \(f(x) = \frac{a}{x + 2} + 1\). 4. Substitute the graph point \(P(1, 0)\): \(0 = \frac{a}{1 + 2} + 1\). Then \(-1 = \frac{a}{3}\), so \(a = -3\). 5. Therefore, \(f(x) = -\frac{3}{x + 2} + 1\).

Answer

a) Vertical asymptote: \(x = -2\); horizontal asymptote: \(y = 1\) b) \(d = -2\) and \(c = 1\) c) \(a = -3\); \(f(x) = -\frac{3}{x + 2} + 1\)
Determine rational functions from conditions 57
The graph shows a translated hyperbola of the form \(f(x) = \frac{a}{x - d} + c\), where \(a \ne 0\). a) Read the equations of the vertical and horizontal asymptotes from the graph. b) Find \(c\) and \(d\). c) Use a point with exact coordinates on the graph to find \(a\). Then write the complete function rule. d) Find the x- and y-intercepts of the graph.
Figure for problem 532216

Hints

- Identify the lines that the graph approaches. - How do those asymptotes determine \(c\) and \(d\)? - Substitute a clearly readable point to find \(a\). - Which input gives the y-intercept? - What equation gives the x-intercept?

Solution

1. The graph approaches the vertical line \(x = 2\) and the horizontal line \(y = 1\), so these are the asymptotes. 2. Therefore, \(d = 2\) and \(c = 1\), giving \(f(x) = \frac{a}{x - 2} + 1\). 3. Substitute the graph point \((4, 3)\): \(3 = \frac{a}{4 - 2} + 1\). Then \(2 = \frac{a}{2}\), so \(a = 4\). Thus, \(f(x) = \frac{4}{x - 2} + 1\). 4. For the y-intercept, set \(x = 0\): \(f(0) = \frac{4}{-2} + 1 = -1\), so the y-intercept is \((0, -1)\). 5. For the x-intercept, solve \(0 = \frac{4}{x - 2} + 1\). Then \(\frac{4}{x - 2} = -1\), so \(x - 2 = -4\) and \(x = -2\). The x-intercept is \((-2, 0)\).

Answer

a) Vertical asymptote: \(x = 2\); horizontal asymptote: \(y = 1\) b) \(d = 2\) and \(c = 1\) c) \(a = 4\); \(f(x) = \frac{4}{x - 2} + 1\) d) y-intercept: \((0, -1)\); x-intercept: \((-2, 0)\)
Determine rational functions from conditions 58
The graph represents a rational function of the form \(f(x) = \frac{a}{x - h} + k\), where \(a \ne 0\). a) Read the vertical and horizontal asymptotes from the graph. b) State the domain of \(f\). c) Use the asymptotes and a point on the graph to determine \(a\), \(h\), and \(k\). Write the function rule.
Figure for problem 532219

Hints

- Identify the vertical and horizontal values approached by the graph. - Exclude the x-value of the vertical asymptote from the domain. - Use the asymptotes to write the function with an unknown \(a\). - Substitute an integer-coordinate point to solve for \(a\).

Solution

1. The graph approaches the vertical line \(x = 2\) and the horizontal line \(y = -1\). 2. Therefore, the domain is \(\mathbb{R} \setminus \{2\}\), and the function has the form \(f(x) = \frac{a}{x - 2} - 1\). 3. The point \((3, 1)\) lies on the graph. Substitution gives \(1 = \frac{a}{3 - 2} - 1\). 4. Solving gives \(a = 2\). 5. Thus, \(h = 2\), \(k = -1\), and \(f(x) = \frac{2}{x - 2} - 1\).

Answer

a) Vertical asymptote: \(x = 2\); horizontal asymptote: \(y = -1\) b) \(\mathbb{R} \setminus \{2\}\) c) \(a = 2\), \(h = 2\), and \(k = -1\); \(f(x) = \frac{2}{x - 2} - 1\)
Determine rational functions from conditions 59
The graph shows a translated hyperbola with function rule \(f(x) = \frac{3}{x - d} + c\). a) Read the excluded input from the graph and state the vertical asymptote. Find \(d\). b) Read the horizontal asymptote from the graph. Find \(c\). c) On which side of the vertical asymptote is the graph below its horizontal asymptote? Explain using your function rule.
Figure for problem 532222

Hints

- Which x-value separates the branches, and what does it tell you about the denominator \(x-d\)? - What height do the branches approach far from that gap? Compare it with the term \(c\). - Once you know the rule, compare the sign of \(f(x)-c\) on either side of the excluded input.

Solution

1. The graph approaches the vertical line \(x = 2\), so the excluded input is \(x = 2\) and the vertical asymptote is \(x = 2\). 2. Since the denominator is \(x - d\), the vertical asymptote gives \(d = 2\). 3. The graph approaches the horizontal line \(y = 1\), so the horizontal asymptote is \(y = 1\) and \(c = 1\). 4. The function rule is \(f(x) = \frac{3}{x - 2} + 1\). 5. Subtract the horizontal asymptote: \(f(x)-1=\frac{3}{x-2}\). This is negative for \(x<2\) and positive for \(x>2\). The left branch lies below \(y=1\).

Answer

a) Excluded input: \(x = 2\); vertical asymptote: \(x = 2\); \(d = 2\) b) Horizontal asymptote: \(y = 1\); \(c = 1\) c) To the left of \(x=2\), since \(f(x)-1=\frac{3}{x-2}<0\) there.
Determine rational functions from conditions 60
The graph represents a rational function of the form \(f(x) = \frac{a}{x - h} + k\). a) Find the equations of the vertical and horizontal asymptotes. b) Determine the function rule for \(f\). c) Find the y-intercept of the graph.
Figure for problem 532225

Hints

- Identify the vertical and horizontal lines the graph approaches. - Use the asymptotes to write the function with an unknown numerator. - Substitute a point on the graph to determine \(a\). - A y-intercept has x-coordinate \(0\).

Solution

1. The graph approaches the vertical line \(x = 3\) and the horizontal line \(y = 2\). 2. Therefore, \(h = 3\), \(k = 2\), and \(f(x) = \frac{a}{x - 3} + 2\). 3. The point \((4, 0)\) lies on the graph. Substitution gives \(0 = \frac{a}{4 - 3} + 2\), so \(a = -2\). 4. Thus, \(f(x) = -\frac{2}{x - 3} + 2\). 5. For the y-intercept, set \(x = 0\): \(f(0) = -\frac{2}{-3} + 2 = \frac{2}{3} + 2 = \frac{8}{3}\). 6. The y-intercept is \(\left(0, \frac{8}{3}\right)\), or approximately \((0, 2.67)\).

Answer

a) Vertical asymptote: \(x = 3\); horizontal asymptote: \(y = 2\) b) \(f(x) = -\frac{2}{x - 3} + 2\) c) \(\left(0, \frac{8}{3}\right)\), approximately \((0, 2.67)\)
Determine rational functions from conditions 61
The graph shows a translated hyperbola. a) Find the equations of the vertical and horizontal asymptotes. b) The function has the form \(f(x) = \frac{a}{x - d} + e\). Find \(a\), \(d\), and \(e\), and write the function rule. c) Find the x- and y-intercepts of the graph.
Figure for problem 532226

Hints

- Which lines does the graph approach without crossing? - How do the asymptotes determine the horizontal and vertical translations? - Use a point with integer coordinates to find the scale factor. - Check the intercepts algebraically against the graph.

Solution

1. The graph approaches the vertical line \(x = -2\) and the horizontal line \(y = 1\), so these are the asymptotes. 2. The asymptotes give \(d = -2\) and \(e = 1\). Thus, \(f(x) = \frac{a}{x + 2} + 1\). 3. Use the exact point \(P(-1, 3)\): \(3 = \frac{a}{-1 + 2} + 1\), so \(a = 2\). Therefore, \(f(x) = \frac{2}{x + 2} + 1\). 4. For the y-intercept, set \(x = 0\): \(f(0) = \frac{2}{2} + 1 = 2\). The y-intercept is \((0, 2)\). 5. For the x-intercept, solve \(0 = \frac{2}{x + 2} + 1\). Then \(\frac{2}{x + 2} = -1\), so \(x + 2 = -2\) and \(x = -4\). The x-intercept is \((-4, 0)\).

Answer

a) Vertical asymptote: \(x = -2\); horizontal asymptote: \(y = 1\) b) \(a = 2\), \(d = -2\), and \(e = 1\); \(f(x) = \frac{2}{x + 2} + 1\) c) y-intercept: \((0, 2)\); x-intercept: \((-4, 0)\)
Determine rational functions from conditions 62
The graph shows a translated hyperbola of the form \(f(x) = \frac{a}{x - d} + e\). a) Find the equations of the asymptotes and determine the function rule \(f(x)\). b) Read the x-intercept and y-intercept from the graph. c) Verify the intercepts from part b) algebraically.
Figure for problem 532228

Hints

- Identify the vertical and horizontal lines the graph approaches. - How do the asymptotes determine \(d\) and \(e\)? - Use a clearly readable point to find \(a\). - Read where the graph crosses each coordinate axis. - Verify an x-intercept by setting the function equal to \(0\), and verify a y-intercept by setting \(x = 0\).

Solution

1. The graph shows the vertical asymptote \(x = 2\) and the horizontal asymptote \(y = 2\), so \(d = 2\) and \(e = 2\). 2. Write \(f(x) = \frac{a}{x - 2} + 2\). Using the point \(P(3, -2)\), \(-2 = \frac{a}{3 - 2} + 2\), so \(a = -4\). Therefore, \(f(x) = -\frac{4}{x - 2} + 2\). 3. From the graph, the x-intercept is \((4, 0)\), and the y-intercept is \((0, 4)\). 4. For the x-intercept, solve \(0 = -\frac{4}{x - 2} + 2\). Then \(2 = \frac{4}{x - 2}\), so \(x - 2 = 2\) and \(x = 4\). 5. For the y-intercept, \(f(0) = -\frac{4}{-2} + 2 = 4\). Both calculations confirm the graph.

Answer

a) Asymptotes: \(x = 2\) and \(y = 2\); \(f(x) = -\frac{4}{x - 2} + 2\) b) x-intercept: \((4, 0)\); y-intercept: \((0, 4)\) c) Solving \(f(x) = 0\) gives \(x = 4\), and \(f(0) = 4\).
Determine rational functions from conditions 63
The graph shows a translated hyperbola of the form \(f(x)=\frac{a}{x-d}+e\), where \(a\ne0\). a) Read the equations of the vertical and horizontal asymptotes. b) Find \(d\) and \(e\). c) Use either marked point \(P\) or \(Q\) to find \(a\), and write the complete function rule.
Figure for problem 532230

Hints

- Identify the vertical and horizontal lines the graph approaches. - How do horizontal and vertical translations determine \(d\) and \(e\)? - Read one marked point from the graph and substitute its coordinates into the partially completed formula.

Solution

1. The graph approaches the vertical line \(x=2\) and the horizontal line \(y=1\). 2. Therefore, \(d=2\) and \(e=1\), so \(f(x)=\frac{a}{x-2}+1\). 3. The graph marks \(P=(4,0)\). Substitute it: \(0=\frac{a}{4-2}+1\). Then \(-1=\frac{a}{2}\), so \(a=-2\). 4. The complete function rule is \(f(x)=-\frac{2}{x-2}+1\). The marked point \(Q=(0,2)\) gives the same value of \(a\).

Answer

a) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=1\) b) \(d=2\) and \(e=1\) c) \(a=-2\); \(f(x)=-\frac{2}{x-2}+1\)
Determine rational functions from conditions 64
The figure shows the graphs of two rational functions, \(f\) and \(g\). a) Find the vertical and horizontal asymptotes of each graph. b) Find a possible function rule for each graph in the forms \(f(x)=d+\frac{a}{x-x_0}\) and \(g(x)=e+\frac{b}{x-x_1}\).
Figure for problem 532478

Hints

- Identify the vertical and horizontal lines each graph approaches. - Use the asymptotes to fill in the translations in the reciprocal-function form. - Substitute a clear point on each graph to find the remaining numerator constant. - Check the resulting rule against the displayed intercept.

Solution

1. For \(f\), the graph shows vertical asymptote \(x=-1\) and horizontal asymptote \(y=1\). Thus, \(f(x)=1+\frac{a}{x+1}\). 2. The graph passes through \((2, 0)\). Substituting gives \(0=1+\frac{a}{3}\), so \(a=-3\). Therefore, \(f(x)=1-\frac{3}{x+1}\). 3. For \(g\), the graph shows vertical asymptote \(x=2\) and horizontal asymptote \(y=-2\). Thus, \(g(x)=-2+\frac{b}{x-2}\). 4. The graph passes through \((4, 0)\). Substituting gives \(0=-2+\frac{b}{2}\), so \(b=4\). Therefore, \(g(x)=-2+\frac{4}{x-2}\).

Answer

a) For \(f\): vertical asymptote \(x=-1\), horizontal asymptote \(y=1\). For \(g\): vertical asymptote \(x=2\), horizontal asymptote \(y=-2\). b) \(f(x)=1-\frac{3}{x+1}\) and \(g(x)=-2+\frac{4}{x-2}\)
Determine rational functions from conditions 65
The graph of a rational function \(f\) is shown. a) Read the horizontal asymptote, vertical asymptote, and zero from the graph. b) Find a function rule in the form \(f(x)=a+\frac{b}{x-c}\). c) Find the x-coordinate where the graph intersects the line \(y=1\).
Figure for problem 532486

Hints

- Identify the horizontal and vertical lines the graph approaches, and locate the x-intercept. - The asymptotes determine \(a\) and \(c\) in the given form. - Substitute the zero to find \(b\). - Set the function equal to \(1\) and solve.

Solution

1. From the graph, the horizontal asymptote is \(y=3\), the vertical asymptote is \(x=2\), and the zero is \(x=-1\). 2. Therefore, \(f(x)=3+\frac{b}{x-2}\). Use \(f(-1)=0\): \(0=3+\frac{b}{-3}\), so \(b=9\). Thus, \(f(x)=3+\frac{9}{x-2}\). 3. Set \(f(x)=1\): \(3+\frac{9}{x-2}=1\). Then \(\frac{9}{x-2}=-2\), so \(x-2=-4.5\) and \(x=-2.5\).

Answer

a) Horizontal asymptote: \(y=3\); vertical asymptote: \(x=2\); zero: \(x=-1\) b) \(f(x)=3+\frac{9}{x-2}\) c) \(x=-2.5\)
Determine rational functions from conditions 66
The figure shows a rational function \(f\) and the line \(g\). a) Read the vertical and horizontal asymptotes of \(f\). b) Use the asymptotes and the marked point \(P\) to find \(f\) in the form \(f(x)=\frac{a}{x-d}+e\). c) The line is \(g(x)=-x+2\). Find the intersections of the two graphs. d) Explain why \(h(x)=f(x)-1\) has no zeros for \(x\ne2\).
Figure for problem 532488

Hints

- What information do the asymptotes give about the unknown parameters? - Read \(P\)'s coordinates from the graph to find the remaining parameter. - Equate the two functions, keeping track of excluded inputs. - Can the numerator of the simplified expression for \(h\) ever be zero?

Solution

1. The vertical asymptote is \(x=2\) and the horizontal asymptote is \(y=1\), so \(f(x)=\frac{a}{x-2}+1\). 2. The plotted point is \(P(1,3)\). Substitution gives \(3=\frac{a}{1-2}+1\), so \(a=-2\) and \(f(x)=-\frac{2}{x-2}+1\). 3. Equate the functions: \(-\frac{2}{x-2}+1=-x+2\), where \(x\ne2\). Multiplying by \(x-2\) gives \(-2=(-x+1)(x-2)=-x^2+3x-2\). 4. Thus, \(x(x-3)=0\), giving \(x=0\) or \(x=3\). The intersection points are \((0,2)\) and \((3,-1)\). 5. Because \(h(x)=-\frac{2}{x-2}\), its numerator is never zero. Hence \(h\) has no zeros.

Answer

a) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=1\). b) \(f(x)=-\frac{2}{x-2}+1\). c) \((0,2)\) and \((3,-1)\). d) \(h(x)=-\frac{2}{x-2}\) cannot equal zero for any allowed \(x\).
Determine rational functions from conditions 67
The graph represents a rational function of the form \(f(x)=\frac{a}{(x-d)^2}+c\), where \(a>0\). a) Use the graph to determine \(a\), \(c\), and \(d\). Explain how the asymptotes and one point on the graph determine the parameters. b) Describe how to transform the graph of \(p(x)=\frac{1}{x^2}\) into the graph of \(f\). c) Find the zeros of \(f\).
Figure for problem 532489

Hints

- Identify the vertical and horizontal asymptotes first. - Connect the asymptotes to the parameters \(d\) and \(c\). - Substitute a clearly readable point to determine \(a\). - Relate each parameter to a transformation of \(\frac{1}{x^2}\). - Set the function equal to \(0\) to find its zeros.

Solution

1. The vertical asymptote is \(x=2\), so \(d=2\). The horizontal asymptote is \(y=-1\), so \(c=-1\). 2. The point \((0, 0)\) lies on the graph. Substituting it gives \(0=\frac{a}{(0-2)^2}-1=\frac{a}{4}-1\), so \(a=4\). 3. Therefore, \(f(x)=\frac{4}{(x-2)^2}-1\). 4. Starting with \(p(x)=\frac{1}{x^2}\), shift right \(2\) units, stretch vertically by a factor of \(4\), and shift down \(1\) unit. 5. To find the zeros, solve \(\frac{4}{(x-2)^2}-1=0\). Then \((x-2)^2=4\), so \(x-2=\pm2\). Thus, \(x=0\) or \(x=4\).

Answer

a) \(a=4\), \(c=-1\), and \(d=2\), so \(f(x)=\frac{4}{(x-2)^2}-1\) b) Shift right \(2\) units, stretch vertically by a factor of \(4\), and shift down \(1\) unit. c) \(x=0\) and \(x=4\)
Determine rational functions from conditions 68
The figure shows rational-function graphs \(f\) and \(g\). a) For \(f\), identify the hole and the vertical asymptote. b) Do the same for \(g\). c) Give one possible rational function rule for each graph, including its holes, in the form \(y=\frac{u(x)}{v(x)}\).
Figure for problem 532493

Hints

- Which missing points are marked by open circles, and where does a curve run sharply up or down? - Find a simpler rational rule that fits each curve away from its hole. - How could you introduce one excluded input without changing the other function values?

Solution

1. Graph \(f\) approaches the vertical line \(x=1\) and has a hole at \((3,2.5)\). 2. The curve follows \(\frac{x+2}{x-1}\) except for \(x=3\). Include a common factor: \(f(x)=\frac{(x+2)(x-3)}{(x-1)(x-3)}=\frac{x^2-x-6}{x^2-4x+3}\). 3. Graph \(g\) approaches the vertical line \(x=-2\) and has a hole at \((1,0)\). 4. The curve follows \(\frac{x-1}{x+2}\) except for \(x=1\). Include a common factor: \(g(x)=\frac{(x-1)^2}{(x+2)(x-1)}=\frac{x^2-2x+1}{x^2+x-2}\). 5. The canceled factors leave holes at the original excluded inputs; the uncanceled denominator factors create the vertical asymptotes.

Answer

a) Hole: \((3,2.5)\); vertical asymptote: \(x=1\). b) Hole: \((1,0)\); vertical asymptote: \(x=-2\). c) \(f(x)=\frac{(x+2)(x-3)}{(x-1)(x-3)}\) and \(g(x)=\frac{(x-1)^2}{(x+2)(x-1)}\).
Determine rational functions from conditions 69
The graph belongs to a rational function \(f(x)=\frac{ax^2+b}{x^2-c}\), where \(a,b,c\) are real numbers. a) Find the domain and all vertical and horizontal asymptotes from the graph. b) Read the marked points \(A\) and \(B\). Use their coordinates and the asymptotes to find \(a\), \(b\), \(c\), and the function rule. c) Find all x- and y-intercepts.
Figure for problem 532496

Hints

- What does the pair of vertical asymptotes tell you about the denominator? - What do the highest-degree terms tell you about the horizontal asymptote? - Read one marked point to find the remaining parameter, then use the other to check.

Solution

1. The vertical asymptotes are \(x=-1\) and \(x=1\), so \(c=1\), and the domain excludes \(-1\) and \(1\). 2. The horizontal asymptote is \(y=2\). Because the numerator and denominator have the same degree, \(a=2\). 3. The marked points are \(A=(0,8)\) and \(B=(2,0)\). Using \(A\), \(8=\frac{b}{-1}\), so \(b=-8\). 4. Therefore, \(f(x)=\frac{2x^2-8}{x^2-1}\), and point \(B\) verifies \(f(2)=0\). 5. The y-intercept is \((0,8)\). Solving \(2x^2-8=0\) gives x-intercepts \((-2,0)\) and \((2,0)\).

Answer

a) Domain: \(\mathbb{R}\setminus\{-1,1\}\); vertical asymptotes: \(x=-1\), \(x=1\); horizontal asymptote: \(y=2\). b) \(A=(0,8)\), \(B=(2,0)\); \(a=2\), \(b=-8\), \(c=1\); \(f(x)=\frac{2x^2-8}{x^2-1}\). c) X-intercepts: \((-2,0)\), \((2,0)\); y-intercept: \((0,8)\).
Determine rational functions from conditions 70
The graph shows a rational function of the form \(f(x)=\frac{a}{x-d}+e\). a) Find \(d\) and \(e\) from the graph. b) Use the marked point \(P\) to find \(a\), then write the complete function rule.
Figure for problem 532595

Hints

- Which vertical and horizontal lines does the graph approach? - How do their locations determine the shifts in the given formula? - Read the point's coordinates from the graph, then substitute them to find the remaining parameter.

Solution

1. The vertical asymptote is \(x=-2\), so \(d=-2\). 2. The horizontal asymptote is \(y=3\), so \(e=3\). 3. Substitute the plotted point \(P=(2,2)\): \(2=\frac{a}{2+2}+3\). 4. Thus, \(-1=\frac{a}{4}\), so \(a=-4\), giving \(f(x)=-\frac{4}{x+2}+3\).

Answer

a) \(d=-2\), \(e=3\). b) \(a=-4\); \(f(x)=-\frac{4}{x+2}+3\).
Determine rational functions from conditions 71
The graph of a rational function \(f\) is shown. a) Read its vertical and horizontal asymptotes. b) The function has the form \(f(x)=\frac{a}{x-d}+c\). Use the asymptotes to find \(d\) and \(c\), then the marked point \(P\) to find \(a\). c) Combine the terms to write the function as one fraction.
Figure for problem 532723

Hints

- Which vertical and horizontal lines does the graph approach? - How do these lines determine the shifts in the proposed function form? - Read point \(P\) on the graph, then substitute its coordinates. - Before combining terms, rewrite the whole-number term with the denominator of the fraction.

Solution

1. The vertical asymptote is \(x=2\), and the horizontal asymptote is \(y=1\). 2. Hence, \(d=2\), \(c=1\), and \(f(x)=\frac{a}{x-2}+1\). 3. Read \(P=(3,3)\) from the graph. Substitution gives \(3=\frac{a}{3-2}+1\), so \(a=2\). 4. Combine fractions: \(f(x)=\frac{2}{x-2}+\frac{x-2}{x-2}=\frac{x}{x-2}\), where \(x\ne2\).

Answer

a) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=1\). b) \(d=2\), \(c=1\), \(a=2\); \(f(x)=\frac{2}{x-2}+1\). c) \(f(x)=\frac{x}{x-2}\), with \(x\ne2\).
Determine rational functions from conditions 72
The graph represents a function of the form \(f(x) = \frac{a}{x - b} + c\). Find the values of \(a\), \(b\), and \(c\).
Figure for problem 533148

Hints

- Use the vertical asymptote to find the value that makes the denominator zero. - Use the horizontal asymptote to determine the vertical translation. - After finding \(b\) and \(c\), substitute the coordinates of a clearly marked point to solve for \(a\).

Solution

1. The graph approaches the vertical line \(x = -2\). Since the denominator is zero when \(x = b\), it follows that \(b = -2\). 2. The graph approaches the horizontal line \(y = -1\), so \(c = -1\). 3. The function now has the form \(f(x) = \frac{a}{x + 2} - 1\). 4. The point \((1, 0)\) lies on the graph. Substitute it: \(0 = \frac{a}{1 + 2} - 1\). 5. Solving \(0 = \frac{a}{3} - 1\) gives \(a = 3\). 6. Therefore, \(a = 3\), \(b = -2\), and \(c = -1\), and the function is \(f(x) = \frac{3}{x + 2} - 1\).

Answer

\(a = 3\), \(b = -2\), and \(c = -1\); \(f(x) = \frac{3}{x + 2} - 1\)
Determine rational functions from conditions 73
The red graph \(g\) is a transformation of the dashed graph \(f(x)=\frac{1}{x^2}\). Describe every transformation and write the function rule for \(g\).
Figure for problem 533158

Hints

- Compare the opening direction of the two rational graphs. - Locate the new vertical and horizontal asymptotes. - Use one point with integer coordinates to determine the vertical scale factor.

Solution

1. The vertical asymptote moves from \(x=0\) to \(x=2\), so the graph shifts right \(2\) units. The horizontal asymptote moves from \(y=0\) to \(y=3\), so the graph shifts up \(3\) units. 2. The branches approach negative infinity near \(x=2\), so the graph is reflected across the x-axis. 3. Write \(g(x)=\frac{a}{(x-2)^2}+3\). The point \((1, 1)\) lies on \(g\), so \(1=\frac{a}{(1-2)^2}+3=a+3\). Thus, \(a=-2\). 4. Therefore, \(g(x)=-\frac{2}{(x-2)^2}+3\). The factor \(-2\) represents a reflection across the x-axis and a vertical stretch by a factor of \(2\).

Answer

Reflect across the x-axis, stretch vertically by a factor of \(2\), shift right \(2\) units, and shift up \(3\) units; \(g(x)=-\frac{2}{(x-2)^2}+3\)
Determine rational functions from conditions 74
The graph represents a function of the form \(f(x) = \frac{a}{x - x_0} + y_0\). a) Find the equations of the asymptotes. Use them to determine \(x_0\) and \(y_0\). b) Read a point from the graph and use it to find \(a\). Then write the complete function rule.
Figure for problem 533286

Hints

- The intersection of the asymptotes gives the translation parameters. - After finding \(x_0\) and \(y_0\), choose a point with integer coordinates and substitute it. - The placement of the branches relative to the asymptotes indicates the sign of \(a\).

Solution

1. The graph approaches the vertical line \(x = -1\), so \(x_0 = -1\). It approaches the horizontal line \(y = -3\), so \(y_0 = -3\). 2. The function now has the form \(f(x) = \frac{a}{x + 1} - 3\). 3. The point \((1, -1)\) lies on the graph. Substitute it: \(-1 = \frac{a}{1 + 1} - 3\). 4. Solving gives \(2 = \frac{a}{2}\), so \(a = 4\). 5. Therefore, the complete function rule is \(f(x) = \frac{4}{x + 1} - 3\).

Answer

a) Asymptotes: \(x = -1\) and \(y = -3\); \(x_0 = -1\) and \(y_0 = -3\) b) Using \((1, -1)\) gives \(a = 4\); \(f(x) = \frac{4}{x + 1} - 3\)
Determine rational functions from conditions 75
The graph represents a function of the form \(g(x) = \frac{a}{x - h} + k\). a) Find the equations of the vertical and horizontal asymptotes. b) Use the asymptotes to find \(h\) and \(k\). c) The graph passes through the origin \(O(0, 0)\). Use this point to find \(a\), and write the complete function rule. d) Find the input for which \(g(x) = -2\). Check your result on the graph.
Figure for problem 533293

Hints

- In the form \(\frac{a}{x - h} + k\), the asymptotes are \(x = h\) and \(y = k\). - Substitute the coordinates of the origin after finding \(h\) and \(k\). - To find an input for a given output, set the function equal to that output and solve for \(x\). - Compare your solution with the graph.

Solution

1. The graph approaches the vertical line \(x = -2\) and the horizontal line \(y = -1\). 2. In the form \(g(x) = \frac{a}{x - h} + k\), the asymptotes are \(x = h\) and \(y = k\). Therefore, \(h = -2\) and \(k = -1\). 3. Substitute \((0, 0)\) into \(g(x) = \frac{a}{x + 2} - 1\): \(0 = \frac{a}{2} - 1\). Thus, \(a = 2\), and \(g(x) = \frac{2}{x + 2} - 1\). 4. Set \(g(x) = -2\): \(-2 = \frac{2}{x + 2} - 1\). Then \(-1 = \frac{2}{x + 2}\), so \(-(x + 2) = 2\) and \(x = -4\). 5. The point \((-4, -2)\) lies on the graph, confirming the result.

Answer

a) Vertical asymptote: \(x = -2\); horizontal asymptote: \(y = -1\) b) \(h = -2\) and \(k = -1\) c) \(a = 2\); \(g(x) = \frac{2}{x + 2} - 1\) d) \(x = -4\)
Determine rational functions from conditions 76
The three graphs have the form \(f(x) = \frac{a}{x + b} + c\). For each graph, determine \(a\), \(b\), and \(c\) using the asymptotes and one readable point.
Figure for problem 533297

Hints

- Use the vertical and horizontal asymptotes to find \(b\) and \(c\). - Remember that a right shift produces a minus sign in the denominator. - Substitute one exact point from each graph to find \(a\).

Solution

1. Graph A has vertical asymptote \(x = 2\), so \(b = -2\), and horizontal asymptote \(y = -1\), so \(c = -1\). Using \((3, 0)\): \(0 = \frac{a}{3 - 2} - 1\), so \(a = 1\). 2. Graph B has vertical asymptote \(x = -3\), so \(b = 3\), and horizontal asymptote \(y = 2\), so \(c = 2\). Using \((-2, 4)\): \(4 = \frac{a}{-2 + 3} + 2\), so \(a = 2\). 3. Graph C has vertical asymptote \(x = 1\), so \(b = -1\), and horizontal asymptote \(y = -2\), so \(c = -2\). Using \((2, -3)\): \(-3 = \frac{a}{2 - 1} - 2\), so \(a = -1\).

Answer

A: \(a = 1\), \(b = -2\), \(c = -1\) B: \(a = 2\), \(b = 3\), \(c = 2\) C: \(a = -1\), \(b = -1\), \(c = -2\)
Determine rational functions from conditions 77
Consider the graphs of functions \(f\) and \(g\). a) Identify the vertical and horizontal asymptotes of each graph. b) Use the marked points \(P\) and \(Q\) to find each function in the form \(y=\frac{a}{x-x_0}+y_0\).
Figure for problem 533299

Hints

- Read the lines each curve approaches and use them to fill in the translation parameters. - Read each marked point and substitute its coordinates into the partly completed rule. - Check whether the signs of the numerator coefficients fit the branch orientations.

Solution

1. For \(f\), the vertical asymptote is \(x=1\), and the horizontal asymptote is \(y=2\). Thus, \(f(x)=\frac{a}{x-1}+2\). 2. Read \(P=(2,3)\). Substituting gives \(3=\frac{a}{2-1}+2\), so \(a=1\) and \(f(x)=\frac{1}{x-1}+2\). 3. For \(g\), the vertical asymptote is \(x=-2\), and the horizontal asymptote is \(y=-1\). Thus, \(g(x)=\frac{a}{x+2}-1\). 4. Read \(Q=(0,-1.5)\). Substituting gives \(-1.5=\frac{a}{2}-1\), so \(a=-1\) and \(g(x)=-\frac{1}{x+2}-1\).

Answer

a) For \(f\): vertical asymptote \(x=1\), horizontal asymptote \(y=2\). For \(g\): vertical asymptote \(x=-2\), horizontal asymptote \(y=-1\). b) \(f(x)=\frac{1}{x-1}+2\); \(g(x)=-\frac{1}{x+2}-1\).
Determine rational functions from conditions 78
The graph shows a translated hyperbola \(h\). a) Write the equations of its asymptotes. b) Determine the function rule for \(h\). c) Find the x-intercept of the function.
Figure for problem 533300

Hints

- Identify the horizontal and vertical lines that the graph approaches. - Substitute the marked point to determine \(a\). - Set the function equal to \(0\) to find the x-intercept.

Solution

1. The graph approaches the vertical line \(x = 3\) and the horizontal line \(y = 1\). 2. Therefore, \(h(x)\) has the form \(h(x) = \frac{a}{x - 3} + 1\). 3. The point \((5, 2)\) lies on the graph. Substitution gives \(2 = \frac{a}{5 - 3} + 1\), so \(1 = \frac{a}{2}\) and \(a = 2\). 4. Thus, \(h(x) = \frac{2}{x - 3} + 1\). 5. To find the x-intercept, set \(h(x) = 0\): \(0 = \frac{2}{x - 3} + 1\). Then \(-1 = \frac{2}{x - 3}\), so \(-(x - 3) = 2\) and \(x = 1\). 6. The x-intercept is \((1, 0)\).

Answer

a) Vertical asymptote: \(x = 3\); horizontal asymptote: \(y = 1\) b) \(h(x) = \frac{2}{x - 3} + 1\) c) \((1, 0)\)
Determine rational functions from conditions 79
The graph represents a function of the form \(f(x) = \frac{a}{x - h} + k\). Determine the function rule.
Figure for problem 533302

Hints

- Use the vertical and horizontal asymptotes to find \(h\) and \(k\). - Remember that a vertical asymptote at a negative input produces a plus sign in the denominator. - Substitute a point from the graph to solve for \(a\). - Verify the rule with a second point if possible.

Solution

1. The vertical asymptote is \(x = -1.5\), so \(h = -1.5\). 2. The horizontal asymptote is \(y = 2.5\), so \(k = 2.5\). 3. The function has the form \(f(x) = \frac{a}{x + 1.5} + 2.5\). 4. The point \((-1, 3.5)\) lies on the graph. Substitute it: \(3.5 = \frac{a}{-1 + 1.5} + 2.5\). 5. This gives \(1 = \frac{a}{0.5}\), so \(a = 0.5\). 6. Therefore, \(f(x) = \frac{0.5}{x + 1.5} + 2.5\).

Answer

\(f(x) = \frac{0.5}{x + 1.5} + 2.5\)
Determine rational functions from conditions 80
Determine the function rule for the graph of \(g\).
Figure for problem 533304

Hints

- Use the vertical asymptote to determine the expression in the denominator. - Use the horizontal asymptote to determine the constant outside the fraction. - Substitute a point on the graph and solve for \(a\). - The locations of the branches relative to the asymptotes indicate whether \(a\) is positive or negative.

Solution

1. The graph approaches the vertical line \(x = -3\) and the horizontal line \(y = -2\). 2. Therefore, the function has the form \(g(x) = \frac{a}{x + 3} - 2\). 3. The point \((-4, 0)\) lies on the graph. Substitute it: \(0 = \frac{a}{-4 + 3} - 2\). 4. This gives \(2 = \frac{a}{-1}\), so \(a = -2\). 5. Thus, \(g(x) = -\frac{2}{x + 3} - 2\).

Answer

\(g(x) = -\frac{2}{x + 3} - 2\)
Determine rational functions from conditions 81
The graph of a rational function \(f\) is shown. A point is marked. a) Use the asymptotes and marked point to find \(f\) in the form \(f(x)=\frac{a}{x-h}+k\). b) Calculate the exact x- and y-intercepts. c) State the domain and range.
Figure for problem 533305

Hints

- Read the two asymptotes to find the shifts in the reciprocal form. - Use the marked point to find the coefficient, then calculate the intercepts from the rule. - Which input is excluded by the denominator, and which output can the function never reach?

Solution

1. The vertical asymptote is \(x=-2\) and the horizontal asymptote is \(y=1\). Thus, \(f(x)=\frac{a}{x+2}+1\). 2. Read the point \((-1,2)\). Substitute: \(2=\frac{a}{1}+1\), so \(a=1\). Therefore, \(f(x)=\frac{1}{x+2}+1\). 3. Set \(f(x)=0\): \(\frac{1}{x+2}+1=0\), so \(x=-3\). The x-intercept is \((-3,0)\). 4. Compute \(f(0)=\frac{1}{2}+1=\frac{3}{2}\). The y-intercept is \(\left(0,\frac{3}{2}\right)\). 5. The denominator excludes \(x=-2\), and the nonzero fractional term prevents \(y=1\). The domain is \(( -\infty,-2)\cup(-2,\infty)\), and the range is \((-\infty,1)\cup(1,\infty)\).

Answer

a) \(f(x)=\frac{1}{x+2}+1\). b) X-intercept: \((-3,0)\); y-intercept: \(\left(0,\frac{3}{2}\right)\). c) Domain: \((-\infty,-2)\cup(-2,\infty)\); range: \((-\infty,1)\cup(1,\infty)\).
Determine rational functions from conditions 82
The graph of \(g\) is a translated hyperbola. a) Find a rule in the form \(g(x)=\frac{a}{x-h}+k\). b) Find its x- and y-intercepts, or explain why one does not exist. Check algebraically.
Figure for problem 533306

Hints

- Which axis or line is the vertical asymptote, and what is the horizontal asymptote? - Use a clearly readable point to determine the remaining coefficient. - Find each intercept from the equation, but first check that the required input is allowed.

Solution

1. The graph has vertical asymptote \(x=0\) and horizontal asymptote \(y=-2\), so \(g(x)=\frac{a}{x}-2\). 2. A readable point is \((1,2)\). Substitute to get \(2=a-2\), so \(a=4\) and \(g(x)=\frac{4}{x}-2\). 3. Set \(g(x)=0\): \(\frac{4}{x}-2=0\). Then \(2x=4\), giving \(x=2\), so the x-intercept is \((2,0)\). 4. A y-intercept would require \(x=0\), which is excluded from the domain, so there is no y-intercept.

Answer

a) \(g(x)=\frac{4}{x}-2\). b) X-intercept: \((2,0)\); no y-intercept because \(x=0\) is excluded.
Determine rational functions from conditions 83
Use the graph of \(g\). a) Write the equations of its vertical and horizontal asymptotes. b) Assume \(g(x) = \frac{a}{x - h} + k\). Use the asymptotes and the marked point to determine the function rule. c) A new function \(p\) is formed by translating the graph of \(g\) \(2\) units right and \(3\) units up. Write a function rule for \(p\).
Figure for problem 533318

Hints

- Identify the vertical and horizontal lines that the graph approaches. - Substitute the marked point after using the asymptotes to write the function with an unknown \(a\). - A translation right changes the input; a translation up changes the output. - Check the sign inside the denominator carefully.

Solution

1. The graph approaches the vertical line \(x = 2\) and the horizontal line \(y = -2\). 2. Therefore, \(g(x) = \frac{a}{x - 2} - 2\). 3. The marked point is \((3, -1)\). Substitution gives \(-1 = \frac{a}{3 - 2} - 2\), so \(a = 1\). Thus, \(g(x) = \frac{1}{x - 2} - 2\). 4. Translating \(2\) units right replaces \(x\) with \(x - 2\), and translating \(3\) units up adds \(3\). Therefore, \(p(x) = g(x - 2) + 3 = \frac{1}{(x - 2) - 2} - 2 + 3 = \frac{1}{x - 4} + 1\).

Answer

a) Vertical asymptote: \(x = 2\); horizontal asymptote: \(y = -2\) b) \(g(x) = \frac{1}{x - 2} - 2\) c) \(p(x) = \frac{1}{x - 4} + 1\)
Determine rational functions from conditions 84
The graph represents a function of the form \(f(x) = \frac{a}{x - h} + k\). a) Find the equations of the vertical and horizontal asymptotes. b) Determine \(h\) and \(k\). c) Use a point with coordinates that can be read clearly from the graph to determine \(a\). Write the complete function rule. d) Find the x-intercept of \(f\).
Figure for problem 533331

Hints

- Identify the values approached by the graph vertically and horizontally. - In \(\frac{a}{x - h} + k\), the asymptotes are \(x = h\) and \(y = k\). - Substitute an integer-coordinate point to solve for \(a\). - At an x-intercept, the function value is \(0\).

Solution

1. The graph approaches the vertical line \(x = -3\) and the horizontal line \(y = -1\). 2. Therefore, \(h = -3\) and \(k = -1\), so \(f(x) = \frac{a}{x + 3} - 1\). 3. The point \((-2, 1)\) lies on the graph. Substitution gives \(1 = \frac{a}{-2 + 3} - 1\), so \(a = 2\). Thus, \(f(x) = \frac{2}{x + 3} - 1\). 4. To find the x-intercept, solve \(0 = \frac{2}{x + 3} - 1\). Then \(1 = \frac{2}{x + 3}\), so \(x + 3 = 2\) and \(x = -1\). 5. The x-intercept is \((-1, 0)\).

Answer

a) Vertical asymptote: \(x = -3\); horizontal asymptote: \(y = -1\) b) \(h = -3\) and \(k = -1\) c) \(a = 2\); \(f(x) = \frac{2}{x + 3} - 1\) d) \((-1, 0)\)
Determine rational functions from conditions 85
The graph shows a rational function \(f\) and a line \(g\), where \(f(x)=\frac{a}{x-h}+k\). a) Use the asymptotes and the marked point \(P\) to find the rule for \(f\). b) Read the coordinates of the intersections of \(f\) and \(g\). c) Determine algebraically whether \(Q(5,3.5)\) lies on the graph of \(f\).
Figure for problem 533335

Hints

- Read the vertical and horizontal asymptotes before using the marked point. - Read \(P\)'s coordinates from the graph, then substitute them into the partly known formula. - At an intersection, both graphs have the same input and output. - To test \(Q\), compare the function output with its given y-coordinate.

Solution

1. The vertical asymptote is \(x=1\), so \(h=1\). The horizontal asymptote is \(y=3\), so \(k=3\). Thus, \(f(x)=\frac{a}{x-1}+3\). 2. The marked point is \(P=(2,5)\). Substituting gives \(5=\frac{a}{2-1}+3\), so \(a=2\) and \(f(x)=\frac{2}{x-1}+3\). 3. The two graphed intersections are \((0,1)\) and \((3,4)\). Both also satisfy the line \(g(x)=x+1\) and the rule for \(f\). 4. Compute \(f(5)=\frac{2}{5-1}+3=3.5\). Therefore, \(Q(5,3.5)\) is on the graph of \(f\).

Answer

a) \(f(x)=\frac{2}{x-1}+3\). b) \((0,1)\) and \((3,4)\). c) Yes, since \(f(5)=3.5\).
Determine rational functions from conditions 86
The graph represents \(f(x)=\frac{k}{x-d}+c\). a) Read the vertical and horizontal asymptotes, then find \(d\) and \(c\). b) Use the marked point \(P\) to find \(k\), then write the complete function rule. c) Calculate the y-intercept from your function rule.
Figure for problem 533457

Hints

- What do the two asymptotes tell you about the unknown shifts? - How can a point on the curve help you determine the remaining coefficient? - Which input do you use to calculate the y-intercept?

Solution

1. The vertical asymptote is \(x=2\), giving \(d=2\); the horizontal asymptote is \(y=1\), giving \(c=1\). 2. The marked point is \(P=(3,3)\). Substitution gives \(3=\frac{k}{3-2}+1\), so \(k=2\) and \(f(x)=\frac{2}{x-2}+1\). 3. At \(x=0\), \(f(0)=\frac{2}{-2}+1=0\). Therefore, the y-intercept is \((0,0)\).

Answer

a) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=1\); \(d=2\), \(c=1\). b) \(k=2\); \(f(x)=\frac{2}{x-2}+1\). c) \((0,0)\).
Determine rational functions from conditions 87
The graph of a function of the form \(f(x) = \frac{a}{x^2} + c\) is shown. Use the horizontal asymptote and one readable point to determine \(a\) and \(c\).
Figure for problem 533654

Hints

- Read the horizontal asymptote to determine the vertical shift. - Choose a point with integer coordinates from the graph. - Substitute that point into the function rule to find \(a\).

Solution

1. The graph approaches \(y = 2\) as \(|x|\) becomes large, so the horizontal asymptote is \(y = 2\). Therefore, \(c = 2\). 2. The point \((1, 3)\) lies on the graph. Substitute it into \(f(x) = \frac{a}{x^2} + 2\): \(3 = \frac{a}{1^2} + 2\). 3. Thus, \(3 = a + 2\), so \(a = 1\).

Answer

\(a = 1\) and \(c = 2\)
Determine rational functions from conditions 88
The graph of \(g\) is a transformation of \(f(x)=\frac{1}{x}\). Find a formula for \(g\).
Figure for problem 534070

Hints

- Identify the vertical and horizontal asymptotes of the transformed graph. - Use them to write \(g(x)=\frac{a}{x-h}+k\). - Substitute a clear point on the graph to find \(a\).

Solution

1. The parent function has asymptotes \(x=0\) and \(y=0\). The graph of \(g\) has asymptotes \(x=2\) and \(y=1\), so \(g(x)=\frac{a}{x-2}+1\). 2. The graph passes through \((3, 3)\). Substitute: \(3=\frac{a}{3-2}+1\), so \(a=2\). 3. Therefore, \(g(x)=\frac{2}{x-2}+1\).

Answer

\(g(x)=\frac{2}{x-2}+1\)
Determine rational functions from conditions 89
The graph shows a rational function of the form \(g(x)=\frac{a}{x-x_0}+c\). a) Read the vertical and horizontal asymptotes, and state \(x_0\) and \(c\). b) Use a clear point on the graph, such as an intercept, to find \(a\). c) Find \(g(6)\).
Figure for problem 534112

Hints

- Identify the asymptotes from the curve and coordinate grid. - Substitute an intercept with exact coordinates to find \(a\). - Evaluate the completed function at \(x=6\). - Check the axis scale before reading coordinates.

Solution

1. The graph shows vertical asymptote \(x=2\), so \(x_0=2\), and horizontal asymptote \(y=1\), so \(c=1\). Thus, \(g(x)=\frac{a}{x-2}+1\). 2. The graph passes through \((0, -1)\). Substituting gives \(-1=\frac{a}{-2}+1\), so \(a=4\). Therefore, \(g(x)=\frac{4}{x-2}+1\). 3. \(g(6)=\frac{4}{6-2}+1=2\).

Answer

a) Vertical asymptote: \(x=2\), so \(x_0=2\); horizontal asymptote: \(y=1\), so \(c=1\) b) \(a=4\), so \(g(x)=\frac{4}{x-2}+1\) c) \(g(6)=2\)
Determine rational functions from conditions 90
The graph of a rational function with a linear numerator and linear denominator is shown. Find a possible function rule \(f(x)\).
Figure for problem 534113

Hints

- Read the vertical and horizontal asymptotes. - Use the horizontal asymptote to determine the ratio of leading coefficients. - Use the x-intercept to find the remaining numerator constant.

Solution

1. The graph has vertical asymptote \(x=1\), so use denominator \(x-1\). 2. The horizontal asymptote is \(y=2\), so use a numerator with leading coefficient \(2\): \(f(x)=\frac{2x+b}{x-1}\). 3. The x-intercept is \(x=-2\), so \(2(-2)+b=0\). Therefore, \(b=4\). 4. Thus, \(f(x)=\frac{2x+4}{x-1}\). As a check, \(f(0)=-4\), which matches the graph.

Answer

\(f(x)=\frac{2x+4}{x-1}\)
Determine rational functions from conditions 91
The graph of a rational function \(f\) is symmetric about the y-axis. Assuming the function has the form \(f(x)=\frac{x^2+a}{x^2+b}\), find its function rule.
Figure for problem 534114

Hints

- Use the vertical asymptotes to determine the denominator constant. - Use the y-intercept to determine the numerator constant. - Check the horizontal asymptote using the leading coefficients.

Solution

1. The graph has vertical asymptotes at \(x=-1\) and \(x=1\). Since the denominator is \(x^2+b\), the equation \(1+b=0\) gives \(b=-1\). 2. The graph passes through \((0, -1)\). Therefore, \(-1=f(0)=\frac{a}{-1}\), so \(a=1\). 3. Thus, \(f(x)=\frac{x^2+1}{x^2-1}\). The equal leading coefficients also give horizontal asymptote \(y=1\), matching the graph.

Answer

\(f(x)=\frac{x^2+1}{x^2-1}\)
Determine rational functions from conditions 92
The figure shows a rational function \(f(x)=\frac{a}{x-x_0}+y_0\) and a line \(g\). a) Read the asymptotes and use the marked point \(P\) to find the rule for \(f\). b) Read two intercepts of the line to find the equation for \(g\). c) Find the intersection points of the two graphs algebraically.
Figure for problem 534123

Hints

- Which lines does the rational curve approach, and what do they tell you about its rule? - Read the marked point and both line intercepts directly from the graph. - Equate the function rules and clear the denominator, but exclude values that make it zero.

Solution

1. The asymptotes of \(f\) are \(x=1\) and \(y=1\), so \(f(x)=\frac{a}{x-1}+1\). 2. The plotted point \(P=(2,5)\) gives \(5=\frac{a}{2-1}+1\), hence \(a=4\) and \(f(x)=\frac{4}{x-1}+1\). 3. The line crosses the axes at \((0,7)\) and \((7,0)\). Its slope is \(-1\), so \(g(x)=-x+7\). 4. Set the two expressions equal: \(\frac{4}{x-1}+1=-x+7\) with \(x\ne1\). Multiply to get \(4=(-x+6)(x-1)=-x^2+7x-6\). 5. This gives \(x^2-7x+10=(x-2)(x-5)=0\), so the input values are \(2\) and \(5\). Substitution into \(g\) gives the points \((2,5)\) and \((5,2)\).

Answer

a) \(f(x)=\frac{4}{x-1}+1\). b) \(g(x)=-x+7\). c) \((2,5)\) and \((5,2)\).
Determine rational functions from conditions 93
The graph of a rational function \(f\) is shown. a) Find the vertical asymptote and the coordinates of the hole. b) Give one possible rule in the form \(f(x)=\frac{(x-x_1)(x-x_2)}{(x-x_3)(x-x_4)}\).
Figure for problem 534129

Hints

- Where does the curve get very high or low near one vertical line? - What does the open circle tell you about the graph? - Find a numerator factor for the x-intercept and a common factor for the hole.

Solution

1. The graph grows sharply up and down near \(x=1\), so the vertical asymptote is \(x=1\). 2. The open circle marks a hole at \((3,2)\). 3. The graph has x-intercept \(x=-1\) and horizontal asymptote \(y=1\). 4. Use \(x+1\) in the numerator for the zero, \(x-1\) in the denominator for the vertical asymptote, and \(x-3\) as a common factor to produce the hole. 5. One possible rule is \(f(x)=\frac{(x+1)(x-3)}{(x-1)(x-3)}\), with \(x\ne1,3\). The simplified expression has value \(\frac{3+1}{3-1}=2\) at the hole's x-coordinate, confirming its height.

Answer

a) Vertical asymptote: \(x=1\); hole: \((3,2)\). b) \(f(x)=\frac{(x+1)(x-3)}{(x-1)(x-3)}\), with \(x\ne1,3\).
Determine rational functions from conditions 94
The graph of a rational function \(f\) is shown. a) Find its domain and range. b) Give its vertical and horizontal asymptotes. c) Find one possible function rule using the marked points \(A\) and \(B\).
Figure for problem 534137

Hints

- Find the vertical and horizontal lines the branches approach. - Use these lines to write a translated reciprocal rule with one unknown coefficient. - Read either marked point to find that coefficient; use the other to check.

Solution

1. The graph has vertical asymptote \(x=2\), so the domain excludes \(2\). Its horizontal asymptote is \(y=2\), which this translated reciprocal curve never reaches, so the range excludes \(2\). 2. Thus, the domain and range are both \((-\infty,2)\cup(2,\infty)\). 3. Write \(f(x)=\frac{a}{x-2}+2\). Read \(A=(0,1.5)\); substitution gives \(1.5=\frac{a}{-2}+2\), so \(a=1\). 4. Therefore, \(f(x)=\frac{1}{x-2}+2=\frac{2x-3}{x-2}\). The other marked point \(B=(1.5,0)\) confirms the result because \(f(1.5)=0\).

Answer

a) Domain and range: \((-\infty,2)\cup(2,\infty)\). b) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=2\). c) \(f(x)=\frac{2x-3}{x-2}\).
Determine rational functions from conditions 95
The graph of a rational function \(g\) is shown. a) Find its domain and all asymptotes. b) Find a simple possible rule using the graph's symmetry, the vertical asymptotes, and the marked y-intercept \(S_y\).
Figure for problem 534138

Hints

- Read the two excluded inputs and the horizontal value approached by the branches. - What kind of powers keep a function unchanged when \(x\) is replaced by \(-x\)? - Read the marked y-intercept to determine the remaining numerator constant.

Solution

1. The vertical asymptotes are \(x=-2\) and \(x=2\), so the domain is \((-\infty,-2)\cup(-2,2)\cup(2,\infty)\). The horizontal asymptote is \(y=2\). 2. Because the graph is symmetric about the y-axis, use even powers: \(g(x)=\frac{2x^2+b}{x^2-4}\). The ratio of leading coefficients is \(2\), as required. 3. Read \(S_y=(0,-0.5)\). Substitution gives \(-0.5=\frac{b}{-4}\), so \(b=2\). 4. Thus, one possible rule is \(g(x)=\frac{2x^2+2}{x^2-4}\). The numerator is nonzero at both excluded inputs, confirming the vertical asymptotes.

Answer

a) Domain: \((-\infty,-2)\cup(-2,2)\cup(2,\infty)\); vertical asymptotes: \(x=-2\) and \(x=2\); horizontal asymptote: \(y=2\). b) \(g(x)=\frac{2x^2+2}{x^2-4}\).
Determine rational functions from conditions 96
The figure shows a family of hyperbolas with the same shape but different vertical asymptotes. Find an equation for the family \(f_k(x)\).
Figure for problem 534395

Hints

- Identify the vertical asymptote of each reciprocal graph. - Use a horizontal shift of \(\frac{1}{x}\). - Substitute a clearly visible point to find the numerator.

Solution

1. A horizontally translated reciprocal function has the form \(f_k(x)=\frac{c}{x-k}\), with vertical asymptote \(x=k\). 2. The shown asymptotes are \(x=-3\), \(x=0\), and \(x=3\), which correspond to different values of \(k\). 3. The graph with asymptote \(x=0\) passes through \((1, 2)\), so \(2=\frac{c}{1}\) and \(c=2\). 4. Therefore, the family is \(f_k(x)=\frac{2}{x-k}\).

Answer

\(f_k(x)=\frac{2}{x-k}\)
Determine rational functions from conditions 97
The graph of a rational function \(f\) is shown. a) Find its rule in the form \(f(x)=\frac{a}{x-b}+c\). b) Find the domain and the vertical and horizontal asymptotes. c) State the intervals where \(f\) is increasing or decreasing.
Figure for problem 534542

Hints

- Read the two asymptotes and use them to find the shifts in the reciprocal rule. - Read the marked point to find the coefficient. - Compare the branch directions with the parent graph \(\frac{1}{x}\).

Solution

1. The vertical asymptote is \(x=2\), so \(b=2\), and the horizontal asymptote is \(y=1\), so \(c=1\). 2. The marked point is \(P=(3,2)\). Thus, \(2=\frac{a}{3-2}+1\), giving \(a=1\) and \(f(x)=\frac{1}{x-2}+1\). 3. The domain is \((-\infty,2)\cup(2,\infty)\). The asymptotes are \(x=2\) and \(y=1\). 4. The parent function \(\frac{1}{x}\) decreases on each side of its vertical asymptote. Translations do not change this, so \(f\) decreases on \((-\infty,2)\) and \((2,\infty)\). It has no increasing intervals.

Answer

a) \(f(x)=\frac{1}{x-2}+1\). b) Domain: \((-\infty,2)\cup(2,\infty)\); vertical asymptote \(x=2\); horizontal asymptote \(y=1\). c) Decreasing on \((-\infty,2)\) and \((2,\infty)\); no increasing intervals.
Determine rational functions from conditions 98
The graph of a rational function \(f(x)=\frac{ax+b}{x-c}\) is shown. Use its asymptotes and intercepts to find \(a\), \(b\), and \(c\).
Figure for problem 534866

Hints

- The vertical asymptote determines the denominator zero. - The horizontal asymptote determines the leading-coefficient ratio. - Substitute the y-intercept to find the remaining constant.

Solution

1. The vertical asymptote is \(x=2\), so \(c=2\). 2. The horizontal asymptote is \(y=3\). Since the numerator and denominator have the same degree, the ratio of leading coefficients is \(a=3\). 3. The y-intercept is \((0, 2)\). Therefore, \(2=f(0)=\frac{b}{-2}\), so \(b=-4\). 4. Thus, \(a=3\), \(b=-4\), and \(c=2\).

Answer

\(a=3\), \(b=-4\), \(c=2\)
Determine rational functions from conditions 99
The graph belongs to a rational function \(f(x)=\frac{ax+b}{x+c}\). a) Use the asymptotes and key points to find \(a\), \(b\), and \(c\). b) Check your result by calculating \(f(0)\) and comparing it with the graph.
Figure for problem 534869

Hints

- Read the vertical and horizontal asymptotes first. - Use the horizontal asymptote to determine the leading numerator coefficient. - Use the x-intercept to determine \(b\). - Substitute \(x=0\) to verify the y-intercept.

Solution

1. The vertical asymptote is \(x=-1\), so \(c=1\). 2. The horizontal asymptote is \(y=2\), so the leading-coefficient ratio gives \(a=2\). 3. The x-intercept is \(x=2\). Therefore, \(2\cdot 2+b=0\), so \(b=-4\). Thus, \(f(x)=\frac{2x-4}{x+1}\). 4. Check: \(f(0)=\frac{-4}{1}=-4\), which matches the y-intercept shown on the graph.

Answer

a) \(a=2\), \(b=-4\), \(c=1\) b) \(f(0)=-4\), matching the graph.
Determine rational functions from conditions 100
The graph of a function \(f(x)=\frac{a}{x-b}+c\) is shown. a) Read the asymptotes to find \(b\) and \(c\). b) Use a clear point on the graph to find \(a\). c) Where would the horizontal asymptote be after translating the entire graph 3 units down?
Figure for problem 534870

Hints

- Read the vertical and horizontal asymptotes from the graph. - Choose a graph point whose coordinates are easy to read, then substitute it into the function rule. - How does shifting a graph vertically change its horizontal asymptote?

Solution

1. The vertical asymptote is \(x=1\), so \(b=1\). The horizontal asymptote is \(y=2\), so \(c=2\). 2. The graph passes through the origin. Substitute \((0, 0)\): \(0=\frac{a}{0-1}+2=-a+2\). Therefore, \(a=2\), and \(f(x)=\frac{2}{x-1}+2\). 3. Translating the graph 3 units down also translates the horizontal asymptote 3 units down. Its new equation is \(y=2-3=-1\).

Answer

a) \(b=1\), \(c=2\) b) \(a=2\) c) \(y=-1\)
Determine rational functions from conditions 101
A pottery studio pays a one-time \(\$180\) kiln setup fee plus the same glazing cost for every mug. When it makes \(15\) mugs, the average cost is \(\$24\) per mug. a) Find the glazing cost per mug. b) Write the average cost \(C(n)\) for \(n\) mugs, where \(n\) is a positive whole number. c) What is the fewest mugs the studio can make to bring the average cost down to \(\$18\) or less?

Hints

- How would you express the total cost as a fixed setup charge plus a cost for each mug? - Use the average cost for \(15\) mugs to find the unknown cost per mug. - When you solve for the number of mugs, remember that it must be a positive whole number.

Solution

1. If glazing costs \(c\) dollars per mug, the total cost for \(15\) mugs is \(180+15c\). Thus \(\frac{180+15c}{15}=24\), giving \(c=12\). 2. For \(n>0\), total cost is \(180+12n\), so \(C(n)=\frac{180+12n}{n}=12+\frac{180}{n}\). 3. Solve \(12+\frac{180}{n}\le18\). Since \(n>0\), this gives \(180\le6n\), or \(n\ge30\). The fewest whole mugs is \(30\).

Answer

a) \(\$12\) per mug b) \(C(n)=12+\frac{180}{n}\), for positive whole numbers \(n\) c) \(30\) mugs
Determine rational functions from conditions 102
A hyperbola has lines of symmetry \(s_1: y = x - 2\) and \(s_2: y = -x + 6\). a) Find the intersection of the two lines. What is the significance of this point for the asymptotes of the hyperbola? b) Find the function rule in the form \(f(x) = \frac{k}{x - x_0} + y_0\), given that the graph passes through \(P(2, 1)\).

Hints

- How do you find the common point of two lines? - What does the intersection of the symmetry lines reveal about the center of the hyperbola? - Use the center to identify \(x_0\) and \(y_0\). - Substitute the known point to find \(k\).

Solution

1. Set the line equations equal: \(x - 2 = -x + 6\). Then \(2x = 8\), so \(x = 4\) and \(y = 2\). The intersection is \((4, 2)\). 2. This point is the center of the hyperbola and the intersection of its vertical and horizontal asymptotes. Thus, \(x_0 = 4\) and \(y_0 = 2\). 3. Write \(f(x) = \frac{k}{x - 4} + 2\). 4. Substitute \(P(2, 1)\): \(1 = \frac{k}{2 - 4} + 2\). Then \(-1 = \frac{k}{-2}\), so \(k = 2\). 5. Therefore, \(f(x) = \frac{2}{x - 4} + 2\).

Answer

a) The lines intersect at \((4, 2)\). This point is the center of the hyperbola and the intersection of its asymptotes. b) \(f(x) = \frac{2}{x - 4} + 2\)
Determine rational functions from conditions 103
Find one rational function \(f\) with all three properties. 1. Its only zeros are \(x=-5\) and \(x=3\). 2. It has a vertical asymptote at \(x=0\), with a sign change across the asymptote. 3. Its horizontal asymptote is \(y=4\), approached at both ends of the graph.

Hints

- Use numerator factors for the two required zeros. - How does the power on a denominator factor affect the signs on opposite sides of its zero? - Match the degrees and leading coefficients to obtain the horizontal asymptote \(y=4\).

Solution

1. Use numerator factors \((x+5)\) and \((x-3)\) to create the required zeros. 2. Use an odd power of \(x\) in the denominator to create a vertical asymptote with a sign change at \(x=0\). 3. The numerator and denominator must have the same degree, with leading-coefficient ratio \(4\), so the graph approaches \(y=4\) at both ends. 4. One example is \(f(x)=\frac{4(x-3)(x+5)^2}{x^3}\). Its only zeros are \(-5\) and \(3\), its denominator has an odd-multiplicity zero at \(0\), and its leading-coefficient ratio is \(4\).

Answer

One possible formula is \(f(x)=\frac{4(x-3)(x+5)^2}{x^3}\).
Determine rational functions from conditions 104
A rational function \(h\) has exactly two zeros. Its graph has horizontal asymptote \(y=-0.5\) and exactly one vertical asymptote, \(x=3\). Find one possible formula for \(h\).

Hints

- A nonzero horizontal asymptote can be obtained with equal numerator and denominator degrees. - A repeated denominator zero can create exactly one vertical asymptote. - Choose two distinct numerator zeros that do not cancel the denominator factor. - Set the leading-coefficient ratio equal to \(-0.5\).

Solution

1. Choose numerator and denominator polynomials of degree \(2\) so the function can have two zeros and a nonzero horizontal asymptote. 2. To make \(x=3\) the only vertical asymptote, choose the denominator \((x-3)^2\). 3. The horizontal asymptote \(y=-0.5\) requires a numerator leading coefficient of \(-0.5\). 4. Choose two numerator zeros different from \(3\), such as \(0\) and \(1\). Then the numerator is \(-0.5x(x-1)=-0.5x^2+0.5x\). 5. Therefore, one possible function is \(h(x)=\frac{-0.5x^2+0.5x}{(x-3)^2}\).

Answer

One possible formula is \(h(x)=\frac{-0.5x^2+0.5x}{(x-3)^2}\).
Determine rational functions from conditions 105
A rectangular banner must have exactly \(18\,\text{ft}^2\) of printed area. The design leaves a \(0.5\,\text{ft}\) margin on both the left and right and a \(1\,\text{ft}\) margin on both the top and bottom. a) Let \(x>0\) be the width, in feet, of the printed area. Write the total height of the banner as a function of \(x\). b) Show that the total area of the banner is \(A(x)=\frac{2x^2+20x+18}{x}\) square feet. c) Find the vertical and slant asymptotes of \(A\). d) Find the printed widths for which the total banner area is exactly \(45\,\text{ft}^2\). Round to the nearest hundredth.

Hints

- Sketch the printed rectangle and all four margins. - Use the fixed printed area to express the printed height in terms of the width. - Add both horizontal and vertical margins to obtain the total dimensions. - Rewrite the area function as a linear expression plus a rational remainder.

Solution

1. If the printed height is \(y\), then \(xy=18\), so \(y=\frac{18}{x}\). Including the top and bottom margins, the total height is \(H(x)=\frac{18}{x}+2\). 2. The total width is \(x+1\). Therefore, \(A(x)=(x+1)\left(\frac{18}{x}+2\right)=2x+20+\frac{18}{x}=\frac{2x^2+20x+18}{x}\). 3. Since \(A(x)=2x+20+\frac{18}{x}\), the vertical asymptote is \(x=0\), and the slant asymptote is \(y=2x+20\). 4. Solve \(45=\frac{2x^2+20x+18}{x}\). This gives \(2x^2-25x+18=0\), so \(x=\frac{25\pm\sqrt{481}}{4}\). 5. Both solutions are positive: \(x\approx 0.77\) or \(x\approx 11.73\).

Answer

a) \(H(x)=\frac{18}{x}+2\), for \(x>0\) b) \(A(x)=\frac{2x^2+20x+18}{x}\) c) Vertical asymptote: \(x=0\); slant asymptote: \(y=2x+20\) d) \(x\approx 0.77\,\text{ft}\) or \(x\approx 11.73\,\text{ft}\)
Determine rational functions from conditions 106
The graph shows a translated rational function \(f(x)=\frac{2}{x-b}+c\) and a line \(g\). a) Use the graph to determine \(b\) and \(c\), and write the complete equation of \(f\). b) Determine the equation of \(g\) in the form \(g(x)=mx+n\). c) Calculate the coordinates of the intersections by solving the resulting rational equation.
Figure for problem 532282

Hints

- Identify the vertical and horizontal lines the rational graph approaches. - The vertical asymptote corresponds to the excluded x-value in \(x-b\). - Use two visible points to determine the line. - Set the functions equal and clear the denominator. - Factor the resulting quadratic equation.

Solution

1. The vertical asymptote is \(x=2\), so \(b=2\). The horizontal asymptote is \(y=1\), so \(c=1\). Therefore, \(f(x)=\frac{2}{x-2}+1\). 2. The line passes through \((0,-2)\) and \((2,0)\). Its slope is \(1\), and its y-intercept is \(-2\), so \(g(x)=x-2\). 3. Set the functions equal: \(\frac{2}{x-2}+1=x-2\), with \(x\ne2\). 4. Rearrange and clear the denominator: \(\frac{2}{x-2}=x-3\), so \(2=(x-3)(x-2)\). 5. Expand and simplify: \(x^2-5x+4=0\). Factor: \((x-1)(x-4)=0\), so \(x=1\) or \(x=4\). 6. Substituting into \(g\) gives \((1,-1)\) and \((4,2)\).

Answer

a) \(b=2\), \(c=1\), and \(f(x)=\frac{2}{x-2}+1\) b) \(g(x)=x-2\) c) \((1,-1)\) and \((4,2)\)
Determine rational functions from conditions 107
The figure shows the graphs of two rational functions, \(f\) and \(g\), along with their asymptotes. Find one possible rule for each function. Explain how the visible asymptotes and marked points determine your rules.
Figure for problem 534102

Hints

- Use each vertical asymptote to form the reciprocal denominator. - Use the horizontal or slant asymptote as the non-rational part of the rule. - Substitute one marked point to find the remaining coefficient.

Solution

1. For \(f\), the vertical asymptote is \(x=-3\), and the horizontal asymptote is \(y=2\). Use \(f(x)=2+\frac{k}{x+3}\). 2. The marked point \((-2, 3)\) lies on the graph, so \(3=2+\frac{k}{1}\), giving \(k=1\). Thus, \(f(x)=2+\frac{1}{x+3}\). 3. For \(g\), the vertical asymptote is \(x=4\). The slant asymptote passes through \((0, 1)\) and \((2, 0)\), so its slope is \(-\frac{1}{2}\), and its equation is \(y=-\frac{1}{2}x+1\). 4. Use \(g(x)=-\frac{1}{2}x+1+\frac{c}{x-4}\). The marked point \((5, -2)\) gives \(-2=-\frac{5}{2}+1+c\), so \(c=-\frac{1}{2}\). 5. Therefore, one possible rule is \(g(x)=-\frac{1}{2}x+1-\frac{1}{2(x-4)}\).

Answer

\(f(x)=2+\frac{1}{x+3}\) \(g(x)=-\frac{1}{2}x+1-\frac{1}{2(x-4)}\)
Determine rational functions from conditions 108
The graph shows one member of the family \(h_k(x)=\frac{x^2+kx}{x^2-4}\). a) Find its horizontal asymptote and read where the graph crosses that line. b) Find the value of \(k\) for the displayed graph. c) For which value of \(k\) will the graph of \(h_k\) have a hole at \(x=2\) instead of a vertical asymptote there?
Figure for problem 534116

Hints

- Compare the leading terms to find the horizontal asymptote. - Read where the curve meets that horizontal level and substitute the point. - To create a hole at the excluded input, what must also be zero in the numerator?

Solution

1. Both polynomials have degree \(2\) and leading coefficient \(1\), so the horizontal asymptote is \(y=1\). The displayed graph intersects that line at \((4,1)\). 2. Substitute the intersection: \(1=\frac{16+4k}{16-4}\), so \(16+4k=12\), giving \(k=-1\). 3. A hole at \(x=2\) requires the numerator and denominator both to contain the factor \(x-2\). Therefore, \(4+2k=0\), so \(k=-2\). 4. Indeed, for \(k=-2\), \(h_{-2}(x)=\frac{x(x-2)}{(x-2)(x+2)}\), which agrees with \(\frac{x}{x+2}\) except at the excluded input \(x=2\).

Answer

a) Horizontal asymptote: \(y=1\); crossing: \((4,1)\). b) \(k=-1\). c) \(k=-2\).
Determine rational functions from conditions 109
a) Read every excluded input of \(r\) from the graph. Which one gives a hole, and which give vertical asymptotes? b) Read the x-intercept and the marked point \(P\). Using these features, write one possible factored rule for \(r\). c) Use your rule to find the hole's exact coordinates and the horizontal asymptote.
Figure for problem 561825

Hints

- Distinguish the open point from the lines where the curve rises or falls sharply. - How could the original numerator and denominator produce those different exclusions and the shown x-intercept? - What does the marked point tell you about any overall multiplier in your possible rule? - After canceling a factor, remember that its original input restriction still applies.

Solution

1. The graph has an open circle at \(x=-3\) and vertical asymptotes at \(x=-1\) and \(x=2\). All three inputs are excluded. 2. Its x-intercept is \((1,0)\), and \(P=(0,\frac{1}{2})\). A possible rule is \(r(x)=\frac{a(x+3)(x-1)}{(x+3)(x-2)(x+1)}\). Substituting the marked point gives \(\frac{a}{2}=\frac{1}{2}\), so \(a=1\). 3. For allowed inputs, \(r(x)=\frac{x-1}{(x-2)(x+1)}\). At \(x=-3\), the simplified rule gives \(-\frac{2}{5}\), so the hole is \((-3,-\frac{2}{5})\). The simplified denominator has higher degree, so the horizontal asymptote is \(y=0\).

Answer

a) Excluded: \(x=-3,-1,2\). Hole at \(x=-3\); vertical asymptotes \(x=-1\) and \(x=2\). b) X-intercept: \((1,0)\), \(P=(0,\frac{1}{2})\). One rule is \(r(x)=\frac{(x+3)(x-1)}{(x+3)(x-2)(x+1)}\). c) Hole: \((-3,-\frac{2}{5})\); horizontal asymptote: \(y=0\).

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