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Reciprocal function graphs and transformations

Learning goals

  • Sketches reciprocal parent curves and their transformed graphs.
  • Writes reciprocal function rules for shifts, stretches and reflections.
  • Finds intercepts and asymptotes of a transformed reciprocal curve.
  • Determines the domain and range of a transformed reciprocal curve.
  • Explains the effect of transformation order on a reciprocal function.

Click problems to add them to your worksheet.

Reciprocal function graphs and transformations 1
The graph of \(f(x)=\frac{1}{x}\) is translated 4 units to the right to make the graph of \(g\). Which function rule is \(g\)? a) \(g(x)=\frac{1}{x+4}\) b) \(g(x)=\frac{1}{x-4}\) c) \(g(x)=\frac{1}{x}+4\) d) \(g(x)=\frac{1}{x}-4\)

Hints

- Decide whether a horizontal translation changes the input or the output of the function. - For a right shift, think about which replacement for \(x\) makes the original graph feature at \(x=0\) occur at \(x=4\).

Solution

1. A translation 4 units to the right replaces \(x\) by \(x-4\). 2. Therefore, \(g(x)=\frac{1}{x-4}\).

Answer

b) \(g(x)=\frac{1}{x-4}\)
Reciprocal function graphs and transformations 2
How is the solid rational graph shifted from the dashed parent graph? State the horizontal and vertical shifts.
Figure for problem 561814

Hints

- Compare where the two graphs have their vertical gaps. - Compare the horizontal levels the branches approach. - Use those changes to describe one horizontal and one vertical shift.

Solution

1. The dashed parent graph has asymptotes \(x=0\) and \(y=0\). 2. The solid graph has asymptotes \(x=2\) and \(y=3\). 3. The solid graph is shifted \(2\) units right and \(3\) units up.

Answer

Right \(2\) units and up \(3\) units.
Reciprocal function graphs and transformations 3
The graph of \(y = \frac{12}{x + 2} + 3\) crosses the \(x\)-axis at \(x = a\) and the \(y\)-axis at \(y = b\). Which statement is true? a) \(a = -2\), \(b = 3\) b) \(a = -6\), \(b = 3\) c) \(a = -6\), \(b = 9\) d) \(a = -2\), \(b = 9\)

Hints

- What is the value of \(x\) where a graph crosses the \(y\)-axis? - What is the value of \(y\) where a graph crosses the \(x\)-axis? - Substitute those values into the equation one at a time.

Solution

1. Find the \(y\)-intercept by substituting \(x = 0\): \(y = \frac{12}{0 + 2} + 3 = 6 + 3 = 9\). Therefore, \(b = 9\). 2. Find the \(x\)-intercept by setting \(y = 0\): \(0 = \frac{12}{x + 2} + 3\). 3. Then \(-3 = \frac{12}{x + 2}\), so \(-3(x + 2) = 12\). Thus, \(x + 2 = -4\) and \(x = -6\). Therefore, \(a = -6\). 4. The correct choice is c).

Answer

c) \(a = -6\), \(b = 9\)
Reciprocal function graphs and transformations 4
Consider the function \(h(x) = \frac{12}{x + 4} - 3\). a) Find the \(x\)-intercept. b) Find the \(y\)-intercept. c) For what value of \(x\) is \(h(x) = 1\)?

Hints

- At an \(x\)-intercept, the function value is \(0\). - At a \(y\)-intercept, the input is \(0\). - When solving the equation in part c), first isolate the fraction.

Solution

1. To find the \(x\)-intercept, set \(h(x) = 0\): \(0 = \frac{12}{x + 4} - 3\). Then \(3 = \frac{12}{x + 4}\), so \(3(x + 4) = 12\). Thus, \(x + 4 = 4\) and \(x = 0\). The \(x\)-intercept is \((0, 0)\). 2. To find the \(y\)-intercept, substitute \(x = 0\): \(h(0) = \frac{12}{0 + 4} - 3 = 3 - 3 = 0\). The \(y\)-intercept is also \((0, 0)\). 3. To solve \(h(x) = 1\), write \(1 = \frac{12}{x + 4} - 3\). Then \(4 = \frac{12}{x + 4}\), so \(4(x + 4) = 12\). Thus, \(x + 4 = 3\) and \(x = -1\).

Answer

a) The \(x\)-intercept is \((0, 0)\). b) The \(y\)-intercept is \((0, 0)\). c) \(x = -1\)
Reciprocal function graphs and transformations 5
The supplied graph shows a rational function \(f\) and a line \(g\). Use only the graph for parts a)-c). a) Identify the vertical asymptote of \(f\). b) Identify all intersection points of \(f\) and \(g\). c) At each of \(x=-2\), \(x=1\), and \(x=4\), state whether \(f(x)>g(x)\) or \(f(x)<g(x)\). d) Explain why the x-coordinate of any intersection point is a solution of \(f(x)=g(x)\).
Figure for problem 513104

Hints

- For the vertical asymptote, look for the x-value that the rational branches approach while their y-values grow in magnitude. - Intersection points lie on both graphs. - For each specified x-value, compare which graph is vertically higher. - An intersection means the two functions have the same output at one input.

Solution

1. The branches of \(f\) approach the y-axis without reaching it, so the vertical asymptote is \(x=0\). 2. The two graphs intersect at \((-1,-2)\) and \((2,1)\). 3. At \(x=-2\), the graph of \(f\) is above the graph of \(g\), so \(f(-2)>g(-2)\). At \(x=1\), \(f(1)>g(1)\). At \(x=4\), \(f(4)<g(4)\). 4. At an intersection, both functions have the same y-value at the same x-value. Therefore, that x-coordinate satisfies \(f(x)=g(x)\).

Answer

a) \(x=0\) b) \((-1,-2)\) and \((2,1)\) c) \(f(-2)>g(-2)\); \(f(1)>g(1)\); \(f(4)<g(4)\) d) At an intersection, the functions have equal outputs for the same input, so its x-coordinate satisfies \(f(x)=g(x)\).
Reciprocal function graphs and transformations 6
Consider the function \(g(x) = \frac{2}{x + 1} - 4\). a) Find the vertical asymptote. b) Find the y-intercept. c) Find the zero of the function. d) Describe how the graph of \(g\) is obtained from the graph of \(h(x) = \frac{2}{x}\).

Hints

- When does the denominator equal \(0\)? - What input gives a point on the y-axis? - What equation must be solved to find a zero? - In the form \(\frac{k}{x - x_0} + y_0\), how do \(x_0\) and \(y_0\) affect the graph?

Solution

1. The denominator is \(0\) when \(x + 1 = 0\), so the vertical asymptote is \(x = -1\). 2. Set \(x = 0\): \(g(0) = \frac{2}{1} - 4 = -2\). The y-intercept is \((0, -2)\). 3. Solve \(0 = \frac{2}{x + 1} - 4\). Then \(4 = \frac{2}{x + 1}\), so \(4(x + 1) = 2\). Therefore, \(x + 1 = 0.5\) and \(x = -0.5\). 4. Replacing \(x\) with \(x + 1\) translates the graph \(1\) unit left, and subtracting \(4\) translates it \(4\) units down.

Answer

a) \(x = -1\) b) \((0, -2)\) c) \(x = -0.5\) d) Translate the graph \(1\) unit left and \(4\) units down.
Reciprocal function graphs and transformations 7
The graph of \(g\) is obtained by translating the graph of \(f(x) = \frac{1}{x}\) by \(3\) units left and \(2\) units up. a) Write the function rule for \(g\). b) Write the equations of the vertical and horizontal asymptotes of \(g\). c) Find the y-intercept of the graph of \(g\).

Hints

- How does a horizontal or vertical translation change a function rule? - Which input makes the denominator equal to \(0\)? - Which line does the graph approach as \(|x|\) becomes large? - What input gives the y-intercept?

Solution

1. Translating \(3\) units left replaces \(x\) with \(x + 3\), and translating \(2\) units up adds \(2\). Thus, \(g(x) = \frac{1}{x + 3} + 2\). 2. The denominator is \(0\) at \(x = -3\), so the vertical asymptote is \(x = -3\). The vertical translation gives the horizontal asymptote \(y = 2\). 3. Set \(x = 0\): \(g(0) = \frac{1}{3} + 2 = \frac{7}{3}\). The y-intercept is \(\left(0, \frac{7}{3}\right)\).

Answer

a) \(g(x) = \frac{1}{x + 3} + 2\) b) Vertical asymptote: \(x = -3\); horizontal asymptote: \(y = 2\) c) \(\left(0, \frac{7}{3}\right)\)
Reciprocal function graphs and transformations 8
Consider \(f(x) = \frac{3}{x}\) and \(g(x) = \frac{0.6}{x}\). a) Describe what the graphs have in common about their asymptotes and domains. b) For the same nonzero value of \(x\), which corresponding point lies closer to the origin? Explain using the numerators. c) Evaluate both functions at \(x = 1.5\).

Hints

- Determine which input makes each denominator zero. - Consider what happens to each output as \(|x|\) becomes large. - Compare the absolute values of the numerators for the same input. - Substitute \(x = 1.5\) directly.

Solution

1. Both denominators are zero at \(x = 0\), so each domain is \(\mathbb{R} \setminus \{0\}\). Both graphs have the vertical asymptote \(x = 0\) and the horizontal asymptote \(y = 0\). 2. For the same nonzero \(x\), \(|g(x)| = \frac{0.6}{|x|}\) is less than \(|f(x)| = \frac{3}{|x|}\). The points have the same \(x\)-coordinate, so the point on \(g\) lies closer to the origin. 3. Evaluate: \(f(1.5) = \frac{3}{1.5} = 2\), and \(g(1.5) = \frac{0.6}{1.5} = 0.4\).

Answer

a) Both domains are \(\mathbb{R} \setminus \{0\}\), and both graphs have asymptotes \(x = 0\) and \(y = 0\). b) For the same nonzero \(x\), the point on \(g\) lies closer to the origin because \(0.6 < 3\), so its \(y\)-coordinate has smaller absolute value. c) \(f(1.5) = 2\) and \(g(1.5) = 0.4\)
Reciprocal function graphs and transformations 9
Consider \(h(x) = \frac{2}{x} + 4\) and \(k(x) = \frac{2}{x} - 1\). a) State the horizontal asymptote of each graph. b) Describe the vertical translation that maps the graph of \(h\) onto the graph of \(k\). c) Find the \(x\)-intercept of \(h\).

Hints

- The constant outside the fraction gives the horizontal asymptote. - Compare the two constant terms to determine the translation. - At an \(x\)-intercept, the function value is \(0\).

Solution

1. For a function of the form \(\frac{a}{x} + c\), the horizontal asymptote is \(y = c\). Therefore, the asymptotes are \(y = 4\) for \(h\) and \(y = -1\) for \(k\). 2. The change in the vertical shift is \(-1 - 4 = -5\). Therefore, translating the graph of \(h\) down \(5\) units produces the graph of \(k\). 3. Set \(h(x) = 0\): \(0 = \frac{2}{x} + 4\). Then \(-4 = \frac{2}{x}\), so \(x = -\frac{1}{2}\). The \(x\)-intercept is \(\left(-\frac{1}{2}, 0\right)\).

Answer

a) The horizontal asymptotes are \(y = 4\) for \(h\) and \(y = -1\) for \(k\). b) Translate the graph of \(h\) down \(5\) units. c) The \(x\)-intercept of \(h\) is \(\left(-\frac{1}{2}, 0\right)\).
Reciprocal function graphs and transformations 10
The function \(g(x) = \frac{3}{x + 1} + 2\) has domain \(\mathbb{R} \setminus \{-1\}\). Determine algebraically whether each point lies on the graph. If a point does not lie on the graph, state whether it is above or below the graph: \(P_1(2, 3)\), \(P_2(-2, 1)\), and \(P_3(0, 5)\).

Hints

- What relationship must a point satisfy to lie on a function graph? - Evaluate the function at each given \(x\)-coordinate. - Compare the given \(y\)-coordinate with the calculated function value.

Solution

1. For \(P_1\), \(g(2) = \frac{3}{2 + 1} + 2 = 3\). This equals the given \(y\)-coordinate, so \(P_1\) lies on the graph. 2. For \(P_2\), \(g(-2) = \frac{3}{-2 + 1} + 2 = -1\). Since the point has \(y = 1\) and \(1 > -1\), \(P_2\) lies above the graph. 3. For \(P_3\), \(g(0) = \frac{3}{0 + 1} + 2 = 5\). This equals the given \(y\)-coordinate, so \(P_3\) lies on the graph.

Answer

\(P_1(2, 3)\) and \(P_3(0, 5)\) lie on the graph. Point \(P_2(-2, 1)\) lies above the graph.
Reciprocal function graphs and transformations 11
Consider \(f(x) = \frac{1}{x}\) and \(g(x) = \frac{-3}{x}\). Both graphs have the same asymptotes. a) In which quadrants do the branches of each graph lie? b) For the same nonzero value of \(x\), which corresponding point lies closer to the origin? Justify your answer using the numerator parameters.

Hints

- Test one positive and one negative input for each function. - A negative numerator reflects the graph across the \(x\)-axis. - Compare the absolute output values for the same nonzero input.

Solution

1. For \(f\), positive inputs give positive outputs and negative inputs give negative outputs. Therefore, its branches lie in Quadrants I and III. 2. For \(g\), positive inputs give negative outputs and negative inputs give positive outputs. Therefore, its branches lie in Quadrants II and IV. 3. For the same nonzero \(x\), \(|f(x)| = \frac{1}{|x|}\) and \(|g(x)| = \frac{3}{|x|}\). The points have the same \(x\)-coordinate, but the point on \(f\) has the smaller absolute \(y\)-coordinate. Therefore, the point on \(f\) is closer to the origin.

Answer

a) The branches of \(f\) lie in Quadrants I and III. The branches of \(g\) lie in Quadrants II and IV. b) For the same nonzero \(x\), the point on \(f\) lies closer to the origin because \(\frac{1}{|x|} < \frac{3}{|x|}\).
Reciprocal function graphs and transformations 12
Consider \(f(x) = \frac{1}{x}\), \(g(x) = \frac{5}{x}\), and \(h(x) = -\frac{1}{x}\). a) Describe how the graph of \(g\) differs from the graph of \(f\), including the relative distance of corresponding points from the origin. b) Compare the graphs of \(f\) and \(h\). In which quadrants do their branches lie?

Hints

- Compare the outputs of \(f\) and \(g\) for the same nonzero input. - Determine how a negative sign in front of the entire function changes the graph. - Test one positive and one negative input to identify the quadrants.

Solution

1. For the same nonzero input, \(|g(x)| = \frac{5}{|x|}\) is five times \(|f(x)| = \frac{1}{|x|}\). Thus, the graph of \(g\) is a vertical stretch of the graph of \(f\), and corresponding points on \(g\) lie farther from the origin. 2. The graph of \(h(x) = -\frac{1}{x}\) is a reflection of the graph of \(f\) across the \(x\)-axis. It can also be viewed as a reflection across the \(y\)-axis. 3. The branches of \(f\) lie in Quadrants I and III, while the branches of \(h\) lie in Quadrants II and IV.

Answer

a) The graph of \(g\) is a vertical stretch of the graph of \(f\) by a factor of \(5\); corresponding points lie farther from the origin. b) The graph of \(h\) is a reflection of \(f\). The branches of \(f\) lie in Quadrants I and III, and the branches of \(h\) lie in Quadrants II and IV.
Reciprocal function graphs and transformations 13
Consider \(f(x) = \frac{4}{x - 1} + 3\). One line of symmetry is \(s: y = x + 2\). a) Verify algebraically that \(Q(2, 7)\) lies on the graph of \(f\). b) Reflecting \(Q\) across line \(s\) gives \(R(5, 4)\). Use symmetry to explain why \(R\) must also lie on the hyperbola, and then verify this by substitution.

Hints

- What equation must the coordinates of a point satisfy to lie on a graph? - What happens to a figure when it is reflected across one of its own lines of symmetry? - How can substitution verify the reflected point?

Solution

1. Evaluate \(f(2) = \frac{4}{2 - 1} + 3 = 7\). Therefore, \(Q\) lies on the graph. 2. A reflection across a line of symmetry maps every point of the graph to another point on the same graph. Since \(Q\) lies on the hyperbola, its reflected point \(R\) must also lie on it. 3. Verify by substitution: \(f(5) = \frac{4}{5 - 1} + 3 = 4\). This matches the \(y\)-coordinate of \(R\).

Answer

a) \(f(2) = 7\), so \(Q\) lies on the graph. b) Symmetry implies that the reflection \(R\) also lies on the graph, and \(f(5) = 4\) confirms it.
Reciprocal function graphs and transformations 14
Consider the rational functions \(f(x) = \frac{8}{x + 2} - 2\) and \(g(x) = \frac{-6}{x - 3} - 1\). Find the \(x\)-intercept and the \(y\)-intercept of each graph.

Hints

- To find a \(y\)-intercept, substitute \(x = 0\). - At an \(x\)-intercept, the function value is \(0\). - Isolate the fraction before solving each equation.

Solution

1. For \(f\), substitute \(x = 0\): \(f(0) = \frac{8}{0 + 2} - 2 = 2\). Therefore, the \(y\)-intercept is \((0, 2)\). 2. Set \(f(x) = 0\): \(0 = \frac{8}{x + 2} - 2\). Then \(2 = \frac{8}{x + 2}\), so \(x + 2 = 4\) and \(x = 2\). Therefore, the \(x\)-intercept is \((2, 0)\). 3. For \(g\), substitute \(x = 0\): \(g(0) = \frac{-6}{0 - 3} - 1 = 1\). Therefore, the \(y\)-intercept is \((0, 1)\). 4. Set \(g(x) = 0\): \(0 = \frac{-6}{x - 3} - 1\). Then \(1 = \frac{-6}{x - 3}\), so \(x - 3 = -6\) and \(x = -3\). Therefore, the \(x\)-intercept is \((-3, 0)\).

Answer

\(f\): \(x\)-intercept \((2, 0)\); \(y\)-intercept \((0, 2)\). \(g\): \(x\)-intercept \((-3, 0)\); \(y\)-intercept \((0, 1)\).
Reciprocal function graphs and transformations 15
Consider the function \(f(x) = \frac{4}{x - 1} + 2\). Find the coordinates of the \(x\)-intercept and the \(y\)-intercept.

Hints

- At a \(y\)-intercept, the input is \(0\). - At an \(x\)-intercept, the function value is \(0\). - Isolate the fraction before clearing the denominator.

Solution

1. To find the \(y\)-intercept, substitute \(x = 0\): \(f(0) = \frac{4}{0 - 1} + 2 = -4 + 2 = -2\). Therefore, the \(y\)-intercept is \((0, -2)\). 2. To find the \(x\)-intercept, set \(f(x) = 0\): \(0 = \frac{4}{x - 1} + 2\). 3. Then \(-2 = \frac{4}{x - 1}\), so \(-2(x - 1) = 4\). Thus, \(-2x + 2 = 4\), giving \(x = -1\). 4. Therefore, the \(x\)-intercept is \((-1, 0)\).

Answer

The \(x\)-intercept is \((-1, 0)\), and the \(y\)-intercept is \((0, -2)\).
Reciprocal function graphs and transformations 16
Find the \(x\)-intercept and the \(y\)-intercept of \(h(x) = \frac{15}{x + 3} - 2.5\).

Hints

- At an \(x\)-intercept, the function value is \(0\). - At a \(y\)-intercept, the input is \(0\). - Keep track of the decimal value when you isolate the denominator.

Solution

1. To find the \(y\)-intercept, substitute \(x = 0\): \(h(0) = \frac{15}{0 + 3} - 2.5 = 5 - 2.5 = 2.5\). Therefore, the \(y\)-intercept is \((0, 2.5)\). 2. To find the \(x\)-intercept, set \(h(x) = 0\): \(0 = \frac{15}{x + 3} - 2.5\). 3. Then \(2.5 = \frac{15}{x + 3}\), so \(2.5(x + 3) = 15\). Thus, \(x + 3 = 6\), giving \(x = 3\). 4. Therefore, the \(x\)-intercept is \((3, 0)\).

Answer

The \(x\)-intercept is \((3, 0)\), and the \(y\)-intercept is \((0, 2.5)\).
Reciprocal function graphs and transformations 17
Consider the rational function \(f(x) = \frac{8}{x - 2} - 1\). a) Find the \(x\)-intercept and the \(y\)-intercept of the graph. b) Determine algebraically whether \(P(6, 1)\) lies on the graph.

Hints

- Use \(x = 0\) to find the \(y\)-intercept and \(f(x) = 0\) to find the \(x\)-intercept. - A point lies on a graph when its coordinates satisfy the function equation. - Substitute the point's \(x\)-coordinate and compare the result with its \(y\)-coordinate.

Solution

1. For the \(y\)-intercept, substitute \(x = 0\): \(f(0) = \frac{8}{0 - 2} - 1 = -4 - 1 = -5\). Therefore, the \(y\)-intercept is \((0, -5)\). 2. For the \(x\)-intercept, set \(f(x) = 0\): \(0 = \frac{8}{x - 2} - 1\). Then \(1 = \frac{8}{x - 2}\), so \(x - 2 = 8\) and \(x = 10\). Therefore, the \(x\)-intercept is \((10, 0)\). 3. To test \(P(6, 1)\), evaluate \(f(6)\): \(f(6) = \frac{8}{6 - 2} - 1 = 2 - 1 = 1\). 4. The calculated value matches the point's \(y\)-coordinate, so \(P(6, 1)\) lies on the graph.

Answer

a) The \(x\)-intercept is \((10, 0)\), and the \(y\)-intercept is \((0, -5)\). b) Yes. Since \(f(6) = 1\), the point \(P(6, 1)\) lies on the graph.
Reciprocal function graphs and transformations 18
Consider the functions \(f(x) = \frac{6}{x + 2} - 1.5\) and \(g(x) = \frac{-4}{x - 5} + 0.8\). Find the \(x\)-intercept and the \(y\)-intercept of each graph. Give each answer as an ordered pair.

Hints

- Substitute \(x = 0\) to find a \(y\)-intercept. - Set the function value equal to \(0\) to find an \(x\)-intercept. - Isolate the fraction before solving for \(x\).

Solution

1. For \(f\), substitute \(x = 0\): \(f(0) = \frac{6}{2} - 1.5 = 1.5\). Therefore, the \(y\)-intercept is \((0, 1.5)\). 2. Set \(f(x) = 0\): \(0 = \frac{6}{x + 2} - 1.5\). Then \(1.5 = \frac{6}{x + 2}\), so \(x + 2 = 4\) and \(x = 2\). Therefore, the \(x\)-intercept is \((2, 0)\). 3. For \(g\), substitute \(x = 0\): \(g(0) = \frac{-4}{-5} + 0.8 = 1.6\). Therefore, the \(y\)-intercept is \((0, 1.6)\). 4. Set \(g(x) = 0\): \(0 = \frac{-4}{x - 5} + 0.8\). Then \(-0.8 = \frac{-4}{x - 5}\), so \(x - 5 = 5\) and \(x = 10\). Therefore, the \(x\)-intercept is \((10, 0)\).

Answer

\(f\): \(x\)-intercept \((2, 0)\); \(y\)-intercept \((0, 1.5)\). \(g\): \(x\)-intercept \((10, 0)\); \(y\)-intercept \((0, 1.6)\).
Reciprocal function graphs and transformations 19
Consider \(g(x) = \frac{6}{x - 3} - 2\). a) Describe the translations that transform the graph of \(p(x) = \frac{6}{x}\) into the graph of \(g\). b) Determine algebraically whether the graph of \(g\) passes through the origin. c) Find the value of \(x\) for which \(g(x) = 1\).

Hints

- How do changes inside and outside a function affect horizontal and vertical position? - What are the coordinates of the origin? - When a function value is given, which variable must be found?

Solution

1. Replacing \(x\) with \(x - 3\) translates the graph \(3\) units right, and subtracting \(2\) translates it \(2\) units down. 2. The origin is \((0, 0)\). Evaluate \(g(0) = \frac{6}{-3} - 2 = -4\). Since \(g(0) \ne 0\), the graph does not pass through the origin. 3. Solve \(1 = \frac{6}{x - 3} - 2\). Then \(3 = \frac{6}{x - 3}\), so \(x - 3 = 2\) and \(x = 5\).

Answer

a) Translate \(3\) units right and \(2\) units down. b) No, because \(g(0) = -4\). c) \(x = 5\)
Reciprocal function graphs and transformations 20
Consider \(g(x) = \frac{1}{x - 2} + 3\). Translate its graph so that the new vertical asymptote is the y-axis and the new horizontal asymptote is the x-axis. a) Describe the translation. b) Write the function rule for the translated function.

Hints

- Identify the current asymptotes. - Recall the equations of the coordinate axes. - Determine how far each asymptote must move to coincide with its corresponding axis.

Solution

1. The original vertical asymptote is \(x = 2\), and the original horizontal asymptote is \(y = 3\). 2. The y-axis has equation \(x = 0\), so the graph must move \(2\) units left. 3. The x-axis has equation \(y = 0\), so the graph must move \(3\) units down. 4. These translations undo the original shifts, giving the parent function \(g_{\text{new}}(x) = \frac{1}{x}\).

Answer

a) Translate \(2\) units left and \(3\) units down. b) \(g_{\text{new}}(x) = \frac{1}{x}\)
Reciprocal function graphs and transformations 21
The graph of \(g\) is a translation of the graph of \(f(x)=\frac{5}{x+3}\). The graph of \(g\) has vertical asymptote \(x=1\) and horizontal asymptote \(y=-4\). Find the horizontal and vertical shifts and write a rule for \(g\).

Hints

- Identify the asymptotes of the original function. - Compare each original asymptote with the corresponding new asymptote. - A horizontal shift changes the input, while a vertical shift changes the output. - Check which input makes the new denominator zero.

Solution

1. The graph of \(f\) has vertical asymptote \(x=-3\) and horizontal asymptote \(y=0\). 2. Moving the vertical asymptote from \(x=-3\) to \(x=1\) requires a shift right \(4\) units. 3. Moving the horizontal asymptote from \(y=0\) to \(y=-4\) requires a shift down \(4\) units. 4. Therefore, \(g(x)=f(x-4)-4=\frac{5}{(x-4)+3}-4=\frac{5}{x-1}-4\).

Answer

Shift right \(4\) units and down \(4\) units. The function is \(g(x)=\frac{5}{x-1}-4\).
Reciprocal function graphs and transformations 22
Consider \(f(x) = \frac{24}{x - 4}\) for \(x > 4\). a) Find \(f(6)\), \(f(8)\), and \(f(12)\). Describe how \(f(x)\) changes as \(x\) increases. b) Without further calculation, explain whether \(f(x)\) can ever equal \(0\) or become negative while \(x > 4\).

Hints

- Substitute the given inputs and compare the outputs. - When does a rational expression equal \(0\)? - What is the sign of \(x - 4\) when \(x > 4\)? - What happens when a fixed positive numerator is divided by an increasing positive denominator?

Solution

1. Evaluate the function: \(f(6) = \frac{24}{6 - 4} = 12\), \(f(8) = \frac{24}{8 - 4} = 6\), and \(f(12) = \frac{24}{12 - 4} = 3\). 2. As \(x\) increases, the positive denominator increases, so the function values decrease. 3. A rational expression can equal \(0\) only when its numerator equals \(0\). Since the numerator is always \(24\), \(f(x)\) cannot equal \(0\). 4. For \(x > 4\), both numerator and denominator are positive, so \(f(x) > 0\). Therefore, the function cannot become negative on the stated domain.

Answer

a) \(f(6) = 12\), \(f(8) = 6\), and \(f(12) = 3\). The function values decrease as \(x\) increases. b) The function can be neither \(0\) nor negative for \(x > 4\).
Reciprocal function graphs and transformations 23
The left panel shows the parent function \(f(x) = \frac{1}{x}\). The right panel shows a translated hyperbola \(g\). a) Read the equations of the vertical and horizontal asymptotes of \(g\). b) Describe the translation that transforms the graph of \(f\) into the graph of \(g\). c) Write the function rule for \(g\).
Figure for problem 532319

Hints

- Identify the vertical and horizontal lines the right-hand graph approaches. - Compare the asymptotes of the translated graph with those of the parent function. - How do horizontal and vertical translations change \(\frac{1}{x}\)? - Pay attention to the sign inside the denominator for a left translation.

Solution

1. The right graph approaches the vertical line \(x = -3\) and the horizontal line \(y = 2\), so these are its asymptotes. 2. The parent graph has asymptotes \(x = 0\) and \(y = 0\). Moving them to \(x = -3\) and \(y = 2\) translates the graph \(3\) units left and \(2\) units up. 3. Therefore, \(g(x) = \frac{1}{x + 3} + 2\).

Answer

a) Vertical asymptote: \(x = -3\); horizontal asymptote: \(y = 2\) b) Translate \(3\) units left and \(2\) units up. c) \(g(x) = \frac{1}{x + 3} + 2\)
Reciprocal function graphs and transformations 24
The two panels show the graphs of rational functions \(g\) and \(h\). Each graph is a translation of the parent function \(f(x) = \frac{1}{x}\). a) Find the equations of the vertical and horizontal asymptotes of \(g\). Then write a function rule for \(g\). b) Find the equations of the vertical and horizontal asymptotes of \(h\). Then write a function rule for \(h\).
Figure for problem 532333

Hints

- Identify the vertical and horizontal lines each graph approaches. - Compare each pair of asymptotes with the asymptotes \(x = 0\) and \(y = 0\) of the parent function. - A horizontal translation changes the expression in the denominator. - A vertical translation adds or subtracts a number outside the fraction.

Solution

1. For \(g\), the graph approaches the vertical line \(x = -2\) and the horizontal line \(y = -1\). 2. Translating \(\frac{1}{x}\) left \(2\) units replaces \(x\) with \(x + 2\). Translating it down \(1\) unit subtracts \(1\). Therefore, \(g(x) = \frac{1}{x + 2} - 1\). 3. For \(h\), the graph approaches the vertical line \(x = 1\) and the horizontal line \(y = 2\). 4. Translating \(\frac{1}{x}\) right \(1\) unit replaces \(x\) with \(x - 1\). Translating it up \(2\) units adds \(2\). Therefore, \(h(x) = \frac{1}{x - 1} + 2\).

Answer

a) Asymptotes: \(x = -2\) and \(y = -1\); \(g(x) = \frac{1}{x + 2} - 1\) b) Asymptotes: \(x = 1\) and \(y = 2\); \(h(x) = \frac{1}{x - 1} + 2\)
Reciprocal function graphs and transformations 25
Let \(f(x)=\frac{2x-6}{x-2}\), with \(x\ne2\). a) Read the vertical and horizontal asymptotes from the graph. b) Find the x- and y-intercepts. c) Rewrite the rule as a constant plus a fraction. Use it to explain the end behavior and the horizontal asymptote.
Figure for problem 532491

Hints

- Which vertical and horizontal lines does the curve approach? - How do you find an x-intercept and a y-intercept from a function rule? - Divide the numerator by the denominator and examine the fractional part for large inputs.

Solution

1. The graph approaches the vertical line \(x=2\) and the horizontal line \(y=2\). 2. The numerator is zero at \(x=3\), so the x-intercept is \((3,0)\). Also, \(f(0)=\frac{-6}{-2}=3\), giving y-intercept \((0,3)\). 3. Divide: \(2x-6=2(x-2)-2\), so \(f(x)=2-\frac{2}{x-2}\). 4. For large positive or negative \(x\), the fraction gets close to zero, so \(f(x)\) approaches \(2\) at both ends. The horizontal asymptote is \(y=2\).

Answer

a) Vertical asymptote: \(x=2\); horizontal asymptote: \(y=2\). b) X-intercept: \((3,0)\); y-intercept: \((0,3)\). c) \(f(x)=2-\frac{2}{x-2}\); both ends approach \(y=2\).
Reciprocal function graphs and transformations 26
The dashed graph is the parent function \(f(x) = \frac{1}{x}\). The solid graph \(g\) is a translation of this function. Find the equations of the asymptotes of \(g\), and write a function rule for \(g\).
Figure for problem 533155

Hints

- Compare the center of the solid hyperbola with the center of the parent graph. - The horizontal asymptote determines the vertical translation. - The vertical asymptote determines the horizontal translation.

Solution

1. The solid graph approaches the vertical line \(x = -2\) and the horizontal line \(y = 2\), so these are its asymptotes. 2. Compared with \(f(x) = \frac{1}{x}\), the graph is translated \(2\) units left and \(2\) units up. 3. A translation \(2\) units left replaces \(x\) with \(x + 2\), and a translation \(2\) units up adds \(2\). Therefore, \(g(x) = \frac{1}{x + 2} + 2\). 4. For example, \(g(-1) = \frac{1}{-1 + 2} + 2 = 3\), which agrees with the graph.

Answer

The asymptotes are \(x = -2\) and \(y = 2\), and \(g(x) = \frac{1}{x + 2} + 2\).
Reciprocal function graphs and transformations 27
Match each graph to the correct function rule. Justify your choices using the asymptotes. 1) \(y = \frac{1}{x - 2} + 1\) 2) \(y = -\frac{1}{x + 1} + 2\) 3) \(y = \frac{1}{x + 2} + 1\) 4) \(y = -\frac{1}{x - 1} + 2\)
Figure for problem 533283

Hints

- Read the vertical asymptote from the denominator shift. - Read the horizontal asymptote from the constant outside the fraction. - Use the branch orientation to determine the sign of the numerator. - Verify a proposed match with one point on the graph.

Solution

1. Graph a) has vertical asymptote \(x = 2\) and horizontal asymptote \(y = 1\). It matches rule 1), \(y = \frac{1}{x - 2} + 1\). 2. Graph b) has vertical asymptote \(x = -1\) and horizontal asymptote \(y = 2\). Its branches have the orientation produced by a negative numerator, so it matches rule 2), \(y = -\frac{1}{x + 1} + 2\).

Answer

a) 1) \(y = \frac{1}{x - 2} + 1\); b) 2) \(y = -\frac{1}{x + 1} + 2\)
Reciprocal function graphs and transformations 28
Match each function rule to the correct graph. Justify each match using the asymptotes. 1) \(f_1(x) = \frac{1}{x + 2} - 1\) 2) \(f_2(x) = \frac{1}{x - 3} + 1\) 3) \(f_3(x) = \frac{1}{x + 1} + 2\) 4) \(f_4(x) = \frac{1}{x - 2} - 2\)
Figure for problem 533296

Hints

- For \(\frac{1}{x - h} + k\), the vertical asymptote is \(x = h\) and the horizontal asymptote is \(y = k\). - Read both asymptotes from each graph before choosing a function. - Pay attention to the sign inside the denominator.

Solution

1. Graph A has vertical asymptote \(x = 3\) and horizontal asymptote \(y = 1\). Therefore, it matches \(f_2(x) = \frac{1}{x - 3} + 1\). 2. Graph B has vertical asymptote \(x = -2\) and horizontal asymptote \(y = -1\). Therefore, it matches \(f_1(x) = \frac{1}{x + 2} - 1\). 3. Graph C has vertical asymptote \(x = 2\) and horizontal asymptote \(y = -2\). Therefore, it matches \(f_4(x) = \frac{1}{x - 2} - 2\). 4. Graph D has vertical asymptote \(x = -1\) and horizontal asymptote \(y = 2\). Therefore, it matches \(f_3(x) = \frac{1}{x + 1} + 2\).

Answer

A: 2); B: 1); C: 4); D: 3)
Reciprocal function graphs and transformations 29
The parent function is \(f(x) = \frac{1}{x}\), and the graph of a translated function \(g\) is shown. Find the equations of the asymptotes, describe the translation, and write the function rule for \(g\).
Figure for problem 533581

Hints

- Identify the lines approached by the translated graph. - Compare the intersection of those asymptotes with the origin. - A right translation produces a minus sign inside the denominator.

Solution

1. The graph approaches the vertical line \(x = 1\) and the horizontal line \(y = 2\). 2. Compared with the parent function, the graph is translated \(1\) unit right and \(2\) units up. 3. A translation \(1\) unit right replaces \(x\) with \(x - 1\), and a translation \(2\) units up adds \(2\). 4. Therefore, \(g(x) = \frac{1}{x - 1} + 2\).

Answer

The asymptotes are \(x = 1\) and \(y = 2\). The graph is translated \(1\) unit right and \(2\) units up, so \(g(x) = \frac{1}{x - 1} + 2\).
Reciprocal function graphs and transformations 30
The dashed graph is \(f(x)=\frac{1}{x^2}\). The red graph \(g\) is a translated version of \(f\). State the horizontal and vertical translations, and write the function rule for \(g\).
Figure for problem 533583

Hints

- Use the vertical asymptote to determine the horizontal translation. - Use the horizontal asymptote to determine the vertical translation. - Then update the parent function rule to match both shifts.

Solution

1. The vertical asymptote moves from \(x=0\) to \(x=-2\), so the graph shifts left \(2\) units. 2. The horizontal asymptote moves from \(y=0\) to \(y=-1\), so the graph shifts down \(1\) unit. 3. Replacing \(x\) with \(x+2\) shifts the graph left \(2\) units, and subtracting \(1\) shifts it down. 4. Therefore, \(g(x)=\frac{1}{(x+2)^2}-1\).

Answer

Shift left \(2\) units and down \(1\) unit; \(g(x)=\frac{1}{(x+2)^2}-1\)
Reciprocal function graphs and transformations 31
The blue graph is the parent function \(f(x) = \frac{1}{x}\). The graphs \(g\) and \(h\) are translations of \(f\). Determine the function rules for \(g\) and \(h\).
Figure for problem 534051

Hints

- Identify the vertical and horizontal asymptotes of each translated graph. - Compare the intersection of each pair of asymptotes with the origin. - A horizontal translation changes the expression in the denominator.

Solution

1. The graph of \(g\) has vertical asymptote \(x = -2\) and horizontal asymptote \(y = 1\). Therefore, it is translated \(2\) units left and \(1\) unit up. 2. Thus, \(g(x) = \frac{1}{x + 2} + 1\). 3. The graph of \(h\) has vertical asymptote \(x = 3\) and horizontal asymptote \(y = -2\). Therefore, it is translated \(3\) units right and \(2\) units down. 4. Thus, \(h(x) = \frac{1}{x - 3} - 2\).

Answer

\(g(x) = \frac{1}{x + 2} + 1\) \(h(x) = \frac{1}{x - 3} - 2\)
Reciprocal function graphs and transformations 32
A student makes three claims about \(g(x)=-\frac{2}{x+1}+3\): 1) The vertical asymptote is \(x=1\). 2) The horizontal asymptote is \(y=3\). 3) The branch to the right of the vertical asymptote lies above \(y=3\). Which claims are incorrect? Correct them.

Hints

- Find the input that makes the denominator zero. - Separate the vertical shift from the reciprocal term. - Check the sign of the reciprocal term on the right side of the excluded input.

Solution

1. The denominator is zero at \(x=-1\), so claim 1 is incorrect: the vertical asymptote is \(x=-1\). 2. The function is \(-\frac{2}{x+1}\) shifted up \(3\), so the horizontal asymptote is \(y=3\). Claim 2 is correct. 3. For \(x>-1\), the denominator is positive, so \(-\frac{2}{x+1}<0\). The graph lies below \(y=3\) on the right. Claim 3 is incorrect.

Answer

Claims 1 and 3 are incorrect. The vertical asymptote is \(x=-1\), and the right branch lies below \(y=3\). Claim 2 is correct.
Reciprocal function graphs and transformations 33
Relative to graph \(f\), which graph shows a vertical stretch by a factor of \(2\), and which graph shows a shift \(2\) units right? Explain using the graphs' shapes or asymptotes.
Figure for problem 561823

Hints

- Compare which graphs have a vertical gap at the same x-value. - Among those, compare their heights at an allowed shared input. - For the remaining graph, measure the horizontal change in the vertical asymptote's position.

Solution

1. Graphs \(f\) and \(g\) have the same vertical and horizontal asymptotes, but \(g\) is twice as far from the x-axis at each common input. Thus, \(g\) is the vertical stretch. 2. Graph \(h\) has its vertical asymptote at \(x=2\), rather than \(x=0\); it is \(f\) shifted right \(2\) units.

Answer

\(g\): vertical stretch by \(2\). \(h\): shift right \(2\) units.
Reciprocal function graphs and transformations 34
A bike courier needs to cover an \(18\)-mile route. If the ride takes \(t>0\) hours, the required average speed is \(v(t)=\frac{18}{t}\) miles per hour. a) Find the speed for rides lasting \(1.5\) hours and \(3\) hours. b) What horizontal asymptote does the speed graph have? Explain what it means here. c) Why is \(t=0\) not in the domain?

Hints

- Average speed equals distance divided by travel time. - Compare the speeds as the allowed time becomes larger. - What would dividing a positive distance by zero mean in this situation?

Solution

1. Substituting gives \(v(1.5)=\frac{18}{1.5}=12\,\text{mph}\) and \(v(3)=\frac{18}{3}=6\,\text{mph}\). 2. The graph approaches \(y=0\) as \(t\) grows; the required speed becomes smaller for longer trip times but is never zero for finite positive \(t\). 3. At \(t=0\), the rule would divide by zero; a nonzero-distance trip cannot take zero time at finite speed.

Answer

a) \(12\,\text{mph}\) and \(6\,\text{mph}\). b) \(y=0\); longer ride times require a smaller average speed. c) \(t=0\) would make the denominator zero and cannot describe this trip.
Reciprocal function graphs and transformations 35
Two students discuss the graph of \(g(x) = \frac{-2}{x + 3}\). Lucas says, “Because the numerator is negative, the branches lie in Quadrants II and IV of the coordinate system formed by the asymptotes.” Sofia says, “The graph must pass through \(P(-1, -1)\).” a) Determine algebraically whether Sofia is correct. b) Decide whether Lucas correctly describes the orientation of the graph, and briefly justify your answer. c) Find the value of \(x\) for which \(g(x) = -0.5\).

Hints

- How can substitution determine whether a point lies on a graph? - How does the sign of the numerator affect the orientation of a reciprocal graph relative to its asymptotes? - How can you solve an equation when the variable appears in the denominator?

Solution

1. Evaluate the function at \(x = -1\): \(g(-1) = \frac{-2}{-1 + 3} = \frac{-2}{2} = -1\). Therefore, Sofia is correct. 2. Relative to the asymptotes \(x = -3\) and \(y = 0\), a negative numerator places the branches in Quadrants II and IV. Therefore, Lucas is correct. 3. Solve \(\frac{-2}{x + 3} = -0.5\). Multiplying by \(x + 3\) gives \(-2 = -0.5(x + 3)\). Dividing by \(-0.5\) gives \(4 = x + 3\), so \(x = 1\).

Answer

a) Yes. \(g(-1) = -1\). b) Lucas is correct. Since the numerator is negative, the branches lie in Quadrants II and IV relative to the asymptotes. c) \(x = 1\)
Reciprocal function graphs and transformations 36
The parent function is \(h(x) = \frac{1}{x}\). A translated function \(g\) has asymptotes that intersect at \((-3, 2)\). a) Write the function rule for \(g\). b) Find the x-intercept of \(g\). c) Explain without calculating why the graph cannot intersect the line \(y = 2\).

Hints

- The intersection of the asymptotes gives the horizontal and vertical translations. - Set \(g(x) = 0\) to find the x-intercept. - Can a fraction with a nonzero numerator equal \(0\)?

Solution

1. The asymptote intersection \((-3, 2)\) means the vertical asymptote is \(x = -3\) and the horizontal asymptote is \(y = 2\). 2. Translating \(\frac{1}{x}\) \(3\) units left and \(2\) units up gives \(g(x) = \frac{1}{x + 3} + 2\). 3. To find the x-intercept, solve \(0 = \frac{1}{x + 3} + 2\). Then \(-2 = \frac{1}{x + 3}\), so \(-2(x + 3) = 1\). 4. Solving \(-2x - 6 = 1\) gives \(x = -3.5\). The x-intercept is \((-3.5, 0)\). 5. The line \(y = 2\) is the horizontal asymptote. Since \(\frac{1}{x + 3}\) can never equal \(0\), \(g(x)\) can never equal \(2\).

Answer

a) \(g(x) = \frac{1}{x + 3} + 2\) b) \((-3.5, 0)\) c) The term \(\frac{1}{x + 3}\) is never \(0\), so \(g(x)\) never equals \(2\).
Reciprocal function graphs and transformations 37
Consider the function \(h(x) = -\frac{1}{x - 2} + 5\). a) Describe the reflections and translations that transform the graph of \(f(x) = \frac{1}{x}\) into the graph of \(h\). b) State the domain and range of \(h\). c) Find the value of \(x\) for which \(h(x) = 4\).

Hints

- What effect does each number in the function rule have on the parent graph? - Which input is excluded, and which output cannot occur? - Rearrange the equation one step at a time to isolate \(x\).

Solution

1. The negative sign reflects the graph across the x-axis. Replacing \(x\) with \(x - 2\) translates it \(2\) units right, and adding \(5\) translates it \(5\) units up. 2. The denominator cannot equal \(0\), so the domain is \(\mathbb{R} \setminus \{2\}\). The function cannot equal its horizontal asymptote, so the range is \(\mathbb{R} \setminus \{5\}\). 3. Solve \(4 = -\frac{1}{x - 2} + 5\). Then \(-1 = -\frac{1}{x - 2}\), so \(x - 2 = 1\) and \(x = 3\).

Answer

a) Reflect across the x-axis, translate \(2\) units right, and translate \(5\) units up. b) Domain: \(\mathbb{R} \setminus \{2\}\); range: \(\mathbb{R} \setminus \{5\}\) c) \(x = 3\)
Reciprocal function graphs and transformations 38
Consider \(f_1(x) = \frac{4}{x}\) and \(f_2(x) = \frac{4}{x - 2} + 1\). 1) Show algebraically that \(S(4, 1)\) lies on the graph of \(f_1\). 2) Determine whether \(S\) lies above, below, or on the graph of \(f_2\). 3) Find the \(x\)-coordinate of the point on the graph of \(f_2\) whose \(y\)-coordinate is \(5\).

Hints

- Substitute the known input into the appropriate function rule. - What does comparing two \(y\)-values at the same \(x\)-coordinate tell you about vertical position? - How can you solve an equation when the variable is in the denominator? - Check carefully which function is used in each part.

Solution

1. Evaluate \(f_1(4) = \frac{4}{4} = 1\). Therefore, \(S\) lies on the graph of \(f_1\). 2. Evaluate \(f_2(4) = \frac{4}{4 - 2} + 1 = 3\). Since the point has \(y = 1\) and \(1 < 3\), \(S\) lies below the graph of \(f_2\). 3. Solve \(5 = \frac{4}{x - 2} + 1\). Then \(4 = \frac{4}{x - 2}\), so \(x - 2 = 1\) and \(x = 3\).

Answer

1) \(f_1(4) = 1\), so \(S\) lies on the graph of \(f_1\). 2) \(S\) lies below the graph of \(f_2\), because \(f_2(4) = 3\) and \(1 < 3\). 3) \(x = 3\)
Reciprocal function graphs and transformations 39
Consider \(f(x) = \frac{4}{x - 1} + 2\) and \(g(x) = \frac{-4}{x - 1} + 2\). a) State the asymptotes of both graphs. b) Find the \(y\)-intercept of each graph. c) Determine whether the graphs have a common point. If they do, find it; otherwise, justify why not.

Hints

- Compare the denominators and constant terms. - Substitute \(x = 0\) to find the \(y\)-intercepts. - Set the two function rules equal to test for intersections. - A contradiction means there is no common point.

Solution

1. Both functions have the denominator \(x - 1\) and the same vertical shift. Therefore, both graphs have the vertical asymptote \(x = 1\) and the horizontal asymptote \(y = 2\). 2. Evaluate \(f(0)\): \(f(0) = \frac{4}{-1} + 2 = -2\). Thus, the \(y\)-intercept of \(f\) is \((0, -2)\). 3. Evaluate \(g(0)\): \(g(0) = \frac{-4}{-1} + 2 = 6\). Thus, the \(y\)-intercept of \(g\) is \((0, 6)\). 4. To find a common point, solve \(\frac{4}{x - 1} + 2 = \frac{-4}{x - 1} + 2\). Subtracting \(2\) and multiplying by \(x - 1\) gives \(4 = -4\), a contradiction. 5. Therefore, the graphs have no common point. They are reflections of each other across \(y = 2\).

Answer

a) Both graphs have asymptotes \(x = 1\) and \(y = 2\). b) The \(y\)-intercepts are \((0, -2)\) for \(f\) and \((0, 6)\) for \(g\). c) The graphs have no common point because solving \(f(x) = g(x)\) leads to the contradiction \(4 = -4\).
Reciprocal function graphs and transformations 40
Consider the functions \(f(x) = \frac{4}{x - 2} + 2\) and \(g(x) = \frac{-4}{x + 2} - 2\). Find the \(x\)-intercept and the \(y\)-intercept of each graph. Then compare the locations of the intercepts.

Hints

- Find both intercepts for each function systematically. - If substituting \(x = 0\) gives a function value of \(0\), the graph passes through the origin. - Compare the distances and coordinates of the intercepts relative to the origin.

Solution

1. For \(f\), substitute \(x = 0\): \(f(0) = \frac{4}{0 - 2} + 2 = 0\). Therefore, the \(y\)-intercept is \((0, 0)\). 2. Set \(f(x) = 0\): \(0 = \frac{4}{x - 2} + 2\). Then \(-2 = \frac{4}{x - 2}\), so \(-2(x - 2) = 4\), giving \(x = 0\). Thus, the \(x\)-intercept is also \((0, 0)\). 3. For \(g\), substitute \(x = 0\): \(g(0) = \frac{-4}{0 + 2} - 2 = -4\). Therefore, the \(y\)-intercept is \((0, -4)\). 4. Set \(g(x) = 0\): \(0 = \frac{-4}{x + 2} - 2\). Then \(2 = \frac{-4}{x + 2}\), so \(2(x + 2) = -4\), giving \(x = -4\). Thus, the \(x\)-intercept is \((-4, 0)\). 5. The graph of \(f\) passes through the origin. The two intercepts of \(g\) lie on the negative axes, each \(4\) units from the origin; they are reflections of each other across the line \(y = x\).

Answer

\(f\): Both intercepts are at \((0, 0)\). \(g\): The \(x\)-intercept is \((-4, 0)\), and the \(y\)-intercept is \((0, -4)\). Comparison: The graph of \(f\) passes through the origin. The intercepts of \(g\) are each \(4\) units from the origin and are reflections across \(y = x\).
Reciprocal function graphs and transformations 41
Compare the \(x\)-intercepts of \(f(x) = \frac{10}{x - 2} - 4\) and \(g(x) = \frac{10}{x - 4} - 2\). Which function has an \(x\)-intercept farther from the origin? Justify your answer by calculating both intercepts.

Hints

- Set each function equal to \(0\) to find its \(x\)-intercept. - The distance from the origin of a point \((x, 0)\) is \(|x|\). - Compare the absolute values of the two \(x\)-coordinates.

Solution

1. Set \(f(x) = 0\): \(0 = \frac{10}{x - 2} - 4\). Then \(4 = \frac{10}{x - 2}\), so \(x - 2 = 2.5\) and \(x = 4.5\). The \(x\)-intercept is \((4.5, 0)\). 2. Set \(g(x) = 0\): \(0 = \frac{10}{x - 4} - 2\). Then \(2 = \frac{10}{x - 4}\), so \(x - 4 = 5\) and \(x = 9\). The \(x\)-intercept is \((9, 0)\). 3. The distances from the origin are \(|4.5| = 4.5\) and \(|9| = 9\). Since \(9 > 4.5\), the \(x\)-intercept of \(g\) is farther from the origin.

Answer

The \(x\)-intercept of \(f\) is \((4.5, 0)\), and the \(x\)-intercept of \(g\) is \((9, 0)\). Therefore, the intercept of \(g\) is farther from the origin.
Reciprocal function graphs and transformations 42
Consider the functions \(f(x) = \frac{4}{x - 2} + 1\) and \(h(x) = \frac{4}{x - 2} - 1\). a) Find the \(x\)-intercept and the \(y\)-intercept of each graph. b) Compare the intercepts. Why are the \(x\)-intercepts different even though the rational terms are identical?

Hints

- Calculate all four intercepts separately. - The constants outside the fractions produce vertical shifts. - Consider how moving a graph up or down changes where it crosses the \(x\)-axis.

Solution

1. For \(f\), substitute \(x = 0\): \(f(0) = \frac{4}{-2} + 1 = -1\). Therefore, the \(y\)-intercept is \((0, -1)\). 2. Set \(f(x) = 0\): \(0 = \frac{4}{x - 2} + 1\). Then \(-1 = \frac{4}{x - 2}\), so \(x - 2 = -4\) and \(x = -2\). Therefore, the \(x\)-intercept is \((-2, 0)\). 3. For \(h\), substitute \(x = 0\): \(h(0) = \frac{4}{-2} - 1 = -3\). Therefore, the \(y\)-intercept is \((0, -3)\). 4. Set \(h(x) = 0\): \(0 = \frac{4}{x - 2} - 1\). Then \(1 = \frac{4}{x - 2}\), so \(x - 2 = 4\) and \(x = 6\). Therefore, the \(x\)-intercept is \((6, 0)\). 5. The constants \(+1\) and \(-1\) shift the same parent graph vertically in opposite directions. Because each graph is at a different vertical position, it crosses the \(x\)-axis at a different input.

Answer

a) \(f\): \(x\)-intercept \((-2, 0)\), \(y\)-intercept \((0, -1)\); \(h\): \(x\)-intercept \((6, 0)\), \(y\)-intercept \((0, -3)\). b) The constants shift the graphs vertically in opposite directions, so the graphs cross the \(x\)-axis at different inputs.
Reciprocal function graphs and transformations 43
Consider \(f(x) = \frac{4}{x + 2} - 1\). a) Write the equations of the vertical and horizontal asymptotes. b) Find the intercepts of the graph with the coordinate axes. c) Consider \(g(x) = \frac{4}{x + 2}\). Explain why the graph of \(g\) has no x-intercept, while the graph of \(f\) does.

Hints

- When can a rational expression equal \(0\)? - What happens to the function value as \(|x|\) becomes large? - Which input is excluded because it makes the denominator \(0\)? - How does the term \(-1\) translate the graph?

Solution

1. The denominator is \(0\) at \(x = -2\), so the vertical asymptote is \(x = -2\). The horizontal asymptote is \(y = -1\). 2. For the y-intercept, set \(x = 0\): \(f(0) = \frac{4}{2} - 1 = 1\). The y-intercept is \((0, 1)\). 3. For the x-intercept, solve \(0 = \frac{4}{x + 2} - 1\). Then \(1 = \frac{4}{x + 2}\), so \(x + 2 = 4\) and \(x = 2\). The x-intercept is \((2, 0)\). 4. The graph of \(g\) has horizontal asymptote \(y = 0\), and \(\frac{4}{x + 2}\) cannot equal \(0\) because its numerator is nonzero. The graph of \(f\) is translated \(1\) unit down, so it can cross the x-axis, as shown by its zero at \(x = 2\).

Answer

a) Vertical asymptote: \(x = -2\); horizontal asymptote: \(y = -1\) b) y-intercept: \((0, 1)\); x-intercept: \((2, 0)\) c) The expression \(\frac{4}{x + 2}\) cannot equal \(0\), but translating the graph down \(1\) unit produces the zero \(x = 2\) for \(f\).
Reciprocal function graphs and transformations 44
Consider the functions \(f(x) = \frac{2}{x} + 3\) and \(g(x) = \frac{2}{x + 3}\). Analyze the intercepts of both graphs. One graph has no \(y\)-intercept, and the other has no \(x\)-intercept. Match each property to the correct function and justify your answer mathematically.

Hints

- To test for a \(y\)-intercept, determine whether \(x = 0\) is allowed and, if so, evaluate the function there. - A fraction equals \(0\) only when its numerator is \(0\) and its denominator is not \(0\). - Check the domain of each function.

Solution

1. For \(f(x) = \frac{2}{x} + 3\), the domain is \(\mathbb{R} \setminus \{0\}\). Because \(x = 0\) is not allowed, the graph has no \(y\)-intercept. 2. To find the \(x\)-intercept of \(f\), solve \(0 = \frac{2}{x} + 3\). Then \(-3 = \frac{2}{x}\), so \(x = -\frac{2}{3}\). Thus, the \(x\)-intercept is \(\left(-\frac{2}{3}, 0\right)\). 3. For \(g(x) = \frac{2}{x + 3}\), substitute \(x = 0\): \(g(0) = \frac{2}{3}\). Thus, the \(y\)-intercept is \(\left(0, \frac{2}{3}\right)\). 4. The equation \(\frac{2}{x + 3} = 0\) has no solution because a fraction can equal zero only when its numerator is zero, and the numerator is the nonzero constant \(2\). Therefore, \(g\) has no \(x\)-intercept.

Answer

\(f\) has no \(y\)-intercept because \(x = 0\) is excluded from its domain. Its \(x\)-intercept is \(\left(-\frac{2}{3}, 0\right)\). \(g\) has the \(y\)-intercept \(\left(0, \frac{2}{3}\right)\) and no \(x\)-intercept because its numerator is never zero.
Reciprocal function graphs and transformations 45
The function \(h(x) = \frac{12}{x - 3} + q\) has an \(x\)-intercept at \(x = 7\). a) Find \(q\), and then find the \(y\)-intercept of \(h\). b) Explain mathematically why \(j(x) = \frac{12}{x - 3}\), which corresponds to \(q = 0\), has no \(x\)-intercept.

Hints

- At the given \(x\)-intercept, substitute the input and use a function value of \(0\). - A fraction equals \(0\) only when its numerator equals \(0\). - After finding \(q\), substitute \(x = 0\) to find the \(y\)-intercept.

Solution

1. An \(x\)-intercept at \(x = 7\) means \(h(7) = 0\). Substitute: \(0 = \frac{12}{7 - 3} + q = 3 + q\), so \(q = -3\). 2. The function is \(h(x) = \frac{12}{x - 3} - 3\). Substitute \(x = 0\): \(h(0) = \frac{12}{-3} - 3 = -7\). Therefore, the \(y\)-intercept is \((0, -7)\). 3. An \(x\)-intercept of \(j\) would require \(\frac{12}{x - 3} = 0\). A fraction can equal zero only when its numerator is zero, but the numerator is the nonzero constant \(12\). Therefore, the equation has no solution and \(j\) has no \(x\)-intercept.

Answer

a) \(q = -3\), and the \(y\)-intercept is \((0, -7)\). b) The equation \(\frac{12}{x - 3} = 0\) has no solution because its numerator is the nonzero constant \(12\).
Reciprocal function graphs and transformations 46
Consider \(f(x) = \frac{2}{x + 1} + 4\) and \(h(x) = \frac{2}{x - 2} + 1\). a) By how many units horizontally and vertically must the graph of \(f\) be translated to coincide with the graph of \(h\)? b) Find the point on the graph of \(f\) whose \(y\)-coordinate is \(6\).

Hints

- Compare the vertical and horizontal asymptotes of the two functions. - What translation moves the vertical asymptote from \(x = -1\) to \(x = 2\)? - A given \(y\)-coordinate is a given function value; solve for the corresponding input.

Solution

1. The vertical asymptote of \(f\) is \(x = -1\), and that of \(h\) is \(x = 2\). Moving from \(-1\) to \(2\) requires a translation of \(3\) units right. 2. The horizontal asymptote of \(f\) is \(y = 4\), and that of \(h\) is \(y = 1\). Moving from \(4\) to \(1\) requires a translation of \(3\) units down. 3. Solve \(6 = \frac{2}{x + 1} + 4\). Then \(2 = \frac{2}{x + 1}\), so \(x + 1 = 1\) and \(x = 0\). The point is \((0, 6)\).

Answer

a) Translate \(3\) units right and \(3\) units down. b) \((0, 6)\)
Reciprocal function graphs and transformations 47
Consider \(h_1(x) = \frac{2}{x - 1} - 1\) and \(h_2(x) = \frac{-2}{x - 1} + 1\). Determine algebraically whether the graphs have the same \(x\)-intercept and the same \(y\)-intercept. Support your conclusions with coordinates.

Hints

- Calculate the intercepts of each function separately. - Two intercepts are the same only when both coordinates match. - Track the signs carefully.

Solution

1. For \(h_1\), solve \(0 = \frac{2}{x - 1} - 1\). Then \(1 = \frac{2}{x - 1}\), so \(x - 1 = 2\) and \(x = 3\). Its \(x\)-intercept is \((3, 0)\). 2. For \(h_2\), solve \(0 = \frac{-2}{x - 1} + 1\). Then \(-1 = \frac{-2}{x - 1}\), so \(x - 1 = 2\) and \(x = 3\). Its \(x\)-intercept is also \((3, 0)\). 3. Evaluate at \(x = 0\): \(h_1(0) = \frac{2}{-1} - 1 = -3\), so its \(y\)-intercept is \((0, -3)\). 4. Also, \(h_2(0) = \frac{-2}{-1} + 1 = 3\), so its \(y\)-intercept is \((0, 3)\). 5. Therefore, the functions have the same \(x\)-intercept but different \(y\)-intercepts.

Answer

The graphs have the same \(x\)-intercept, \((3, 0)\). They have different \(y\)-intercepts: \((0, -3)\) for \(h_1\) and \((0, 3)\) for \(h_2\).
Reciprocal function graphs and transformations 48
Let \(f(x)=\frac{10}{x-8}-2\), with domain \(\mathbb{R}\setminus\{8\}\). a) Find the vertical and horizontal asymptotes, and describe the monotonicity on each part of the domain. b) A horizontal band of total width \(0.4\) is centered on the horizontal asymptote. (1) Find the smallest threshold \(x_0\) such that every graph point with \(x>x_0\) is inside the band. (2) Find the largest threshold \(x_1\) such that every graph point with \(x<x_1\) is inside the band.

Hints

- Find the denominator zero and the limiting output at large \(|x|\). - Use the behavior of a reciprocal function to determine monotonicity on each branch. - Convert the band condition into an absolute-value inequality.

Solution

1. The denominator is zero at \(x=8\), so the vertical asymptote is \(x=8\). As \(|x|\to\infty\), the fraction approaches \(0\), so the horizontal asymptote is \(y=-2\). 2. The reciprocal term \(\frac{10}{x-8}\) is strictly decreasing on each interval \((-\infty, 8)\) and \((8, \infty)\). Therefore, \(f\) is strictly decreasing on each interval. 3. The band condition is \(|f(x)+2|<0.2\), or \(\left|\frac{10}{x-8}\right|<0.2\). 4. This is equivalent to \(|x-8|>50\), so \(x>58\) or \(x<-42\). 5. Thus, \(x_0=58\) and \(x_1=-42\).

Answer

a) Vertical asymptote: \(x=8\); horizontal asymptote: \(y=-2\). The function is strictly decreasing on \((-\infty, 8)\) and \((8, \infty)\). b) (1) \(x_0=58\) (2) \(x_1=-42\)
Reciprocal function graphs and transformations 49
Show algebraically that vertically compressing the graph of \(f(x) = \frac{6}{x-4} + 2\) by a factor of \(0.5\), then shifting it up \(3\) units, produces the graph of \(g(x) = \frac{3}{x-4} + 4\). State the equations of the asymptotes of \(f\) and \(g\), and explain how the asymptotes change under the transformations.

Hints

- A vertical compression multiplies the entire function value, not just one term. - A vertical shift is added after the compression. - Identify which part of a rational function determines each asymptote. - Consider whether changing only outputs can move a vertical line.

Solution

1. Apply the vertical compression to the entire output: \(h(x) = 0.5f(x) = 0.5\left(\frac{6}{x-4}+2\right) = \frac{3}{x-4}+1\). 2. Shift the graph up \(3\) units: \(h(x)+3 = \frac{3}{x-4}+4 = g(x)\). 3. For \(f\), the denominator is zero at \(x=4\), so the vertical asymptote is \(x=4\). Since \(\frac{6}{x-4}\to 0\) as \(x\to\pm\infty\), the horizontal asymptote is \(y=2\). 4. For \(g\), the vertical asymptote is still \(x=4\), and the horizontal asymptote is \(y=4\). 5. The vertical asymptote does not move because the transformations change only output values. The horizontal asymptote changes from \(y=2\) to \(y=0.5\cdot 2+3=4\).

Answer

The transformation gives \(0.5f(x)+3 = \frac{3}{x-4}+4 = g(x)\). Asymptotes of \(f\): \(x=4\) and \(y=2\). Asymptotes of \(g\): \(x=4\) and \(y=4\). The vertical asymptote is unchanged. The horizontal asymptote is transformed by \(y\mapsto 0.5y+3\), so \(2\mapsto 4\).
Reciprocal function graphs and transformations 50
The graph of \(f(x) = -\frac{1}{x+2}+5\) is vertically stretched by a factor of \(k\) and then shifted vertically by \(d\) units, producing the graph of \(g(x) = -\frac{4}{x+2}+12\). Find \(k\) and \(d\) algebraically. Also explain why \(f\) and \(g\) have the same vertical asymptote.

Hints

- Begin with \(g(x)=kf(x)+d\). - Compare the coefficient of the rational term and then compare the constant terms. - Identify the input value that makes the denominator zero. - Decide whether transformations applied outside the function change its domain.

Solution

1. Write the transformation as \(g(x)=kf(x)+d\): \(g(x)=k\left(-\frac{1}{x+2}+5\right)+d=-\frac{k}{x+2}+5k+d\). 2. Match the rational terms: \(-k=-4\), so \(k=4\). 3. Match the constant terms: \(5k+d=12\). Substituting \(k=4\) gives \(20+d=12\), so \(d=-8\). 4. Both functions are undefined at \(x=-2\). Vertical transformations change outputs but do not change the input value where the denominator is zero, so the vertical asymptote remains \(x=-2\).

Answer

The values are \(k=4\) and \(d=-8\). The vertical asymptote remains \(x=-2\) because vertical scaling and shifting do not change the zero of the denominator.
Reciprocal function graphs and transformations 51
Let \(f(x)=\frac{1}{x}\). Rewrite \(g(x)=\frac{3}{2x+4}-1\) in the form \(g(x)=af(b(x+c))+d\). Then describe one sequence of transformations that produces the graph of \(g\) from the graph of \(f\).

Hints

- Factor the coefficient of \(x\) from the denominator. - Match the resulting input to the form \(b(x+c)\). - An input factor changes horizontal scale, while an outside factor changes vertical scale.

Solution

1. Factor the denominator: \(2x+4=2(x+2)\). 2. Then \(g(x)=3\left(\frac{1}{2(x+2)}\right)-1=3f(2(x+2))-1\). Thus, one representation has \(a=3\), \(b=2\), \(c=2\), and \(d=-1\). 3. Starting with the graph of \(f\), horizontally compress by a factor of \(\frac{1}{2}\), shift left \(2\) units, vertically stretch by a factor of \(3\), and shift down \(1\) unit.

Answer

One valid representation is \(g(x)=3f(2(x+2))-1\). Transformations: horizontally compress by a factor of \(\frac{1}{2}\); shift left \(2\) units; vertically stretch by a factor of \(3\); shift down \(1\) unit.
Reciprocal function graphs and transformations 52
Let \(f(x)=\frac{1}{x}\). Apply the following two transformation sequences. Sequence A: First vertically compress the graph by a factor of \(0.5\), then shift it up \(2\) units. Sequence B: First shift the graph up \(2\) units, then vertically compress the entire graph by a factor of \(0.5\). Write the resulting functions \(g\) and \(h\), and show algebraically that their graphs are not identical.

Hints

- In each sequence, apply the second transformation to the result of the first. - A vertical compression multiplies the entire current output. - Check the two final rules at any allowed input, such as \(x=1\).

Solution

1. For Sequence A, first form \(0.5f(x)\), then add \(2\): \(g(x)=0.5\left(\frac{1}{x}\right)+2=\frac{0.5}{x}+2\). 2. For Sequence B, first form \(f(x)+2\), then multiply the entire output by \(0.5\): \(h(x)=0.5\left(\frac{1}{x}+2\right)=\frac{0.5}{x}+1\). 3. The constant terms differ, so \(g(x)\ne h(x)\) for every \(x\ne 0\). Therefore, the graphs are not identical.

Answer

\(g(x)=\frac{0.5}{x}+2\) and \(h(x)=\frac{0.5}{x}+1\). The functions are not identical because their constant terms differ.
Reciprocal function graphs and transformations 53
Let \(f(x)=\frac{1}{x^2}\). The function \(g\) is defined by \(g(x)=1-\frac{4}{x^2-4x+4}\). Describe one sequence of reflections, stretches or compressions, and shifts that produces the graph of \(g\) from the graph of \(f\).

Hints

- Factor the quadratic expression in the denominator. - Rewrite \(g\) in the form \(af(x-c)+d\). - Match each parameter with its graphical effect. - Pay attention to the negative sign and the constant outside the fraction.

Solution

1. Factor the denominator: \(x^2-4x+4=(x-2)^2\). 2. Rewrite the rule as \(g(x)=-4\left(\frac{1}{(x-2)^2}\right)+1=-4f(x-2)+1\). 3. Shift the graph of \(f\) right \(2\) units. 4. Vertically stretch by a factor of \(4\) and reflect across the x-axis. 5. Shift up \(1\) unit.

Answer

Shift right \(2\) units, vertically stretch by a factor of \(4\), reflect across the x-axis, and shift up \(1\) unit.
Reciprocal function graphs and transformations 54
Show algebraically that horizontally stretching the graph of \(f(x)=\frac{2}{x+4}-3\) by a factor of \(3\), then shifting it up \(4\) units, produces the graph of \(g(x)=\frac{6}{x+12}+1\). Explain how the transformations affect the vertical and horizontal asymptotes.

Hints

- A horizontal stretch changes the input of the function. - A vertical shift is added to the entire function value. - Use the zero of the denominator and the constant term to identify the asymptotes. - Decide which transformation affects each asymptote.

Solution

1. A horizontal stretch by a factor of \(3\) replaces \(x\) with \(\frac{x}{3}\): \(f\left(\frac{x}{3}\right)=\frac{2}{x/3+4}-3\). 2. Simplify: \(\frac{2}{x/3+4}-3=\frac{2}{(x+12)/3}-3=\frac{6}{x+12}-3\). 3. Shift up \(4\) units: \(f\left(\frac{x}{3}\right)+4=\frac{6}{x+12}+1=g(x)\). 4. The vertical asymptote \(x=-4\) is horizontally stretched to \(x=-12\). The horizontal asymptote \(y=-3\) shifts up to \(y=1\).

Answer

\(g(x)=f\left(\frac{x}{3}\right)+4=\frac{6}{x+12}+1\). The vertical asymptote changes from \(x=-4\) to \(x=-12\), and the horizontal asymptote changes from \(y=-3\) to \(y=1\).
Reciprocal function graphs and transformations 55
Let \(h(x)=\frac{1}{x-2}+5\). The graph of \(h\) is first vertically stretched by a factor of \(4\), then shifted left \(3\) units. Write the rule for the resulting function \(k\), and explain the locations of its asymptotes using the transformations.

Hints

- A vertical stretch multiplies the entire function, including its constant term. - A shift left replaces \(x\) with \(x+3\). - Track the horizontal asymptote through the vertical stretch. - Track the vertical asymptote through the horizontal shift.

Solution

1. Vertically stretch the entire output: \(4h(x)=4\left(\frac{1}{x-2}+5\right)=\frac{4}{x-2}+20\). 2. Shift left \(3\) units by replacing \(x\) with \(x+3\): \(k(x)=\frac{4}{(x+3)-2}+20=\frac{4}{x+1}+20\). 3. The original vertical asymptote \(x=2\) shifts left \(3\) units to \(x=-1\). 4. The original horizontal asymptote \(y=5\) is vertically stretched by a factor of \(4\), so it becomes \(y=20\).

Answer

\(k(x)=\frac{4}{x+1}+20\). Its vertical asymptote is \(x=-1\), and its horizontal asymptote is \(y=20\).
Reciprocal function graphs and transformations 56
Consider \(h(x)=\frac{5}{2x-8}-1.5\). Find all asymptotes and the exact x-intercept. Then describe how the graph can be obtained from a basic reciprocal graph of the form \(y=\frac{k}{x}\).

Hints

- Rewrite the denominator by factoring out \(2\). - The horizontal shift appears inside the denominator, while the vertical shift is outside the fraction. - Set the function equal to \(0\) to find the x-intercept.

Solution

1. The denominator is zero at \(x=4\), so the vertical asymptote is \(x=4\). 2. Since \(\frac{5}{2x-8}\to 0\) as \(x\to\pm\infty\), the horizontal asymptote is \(y=-1.5\). 3. To find the x-intercept, solve \(\frac{5}{2x-8}-1.5=0\). Then \(5=1.5(2x-8)\), so \(17=3x\) and \(x=\frac{17}{3}\). 4. Rewrite \(h(x)=\frac{2.5}{x-4}-1.5\). Starting with \(y=\frac{2.5}{x}\), shift the graph \(4\) units right and \(1.5\) units down.

Answer

Vertical asymptote: \(x=4\) Horizontal asymptote: \(y=-1.5\) x-intercept: \(\left(\frac{17}{3}, 0\right)\) Transformation: shift \(y=\frac{2.5}{x}\) right \(4\) units and down \(1.5\) units.
Reciprocal function graphs and transformations 57
Consider \(f(x)=\frac{2x+7}{x+3}\). a) Rewrite the function in the form \(f(x)=c+\frac{a}{x-x_0}\). b) Find the horizontal asymptote, vertical asymptote, and x-intercept. c) Explain which form of the function makes the horizontal asymptote easiest to identify and which form makes the x-intercept easiest to identify.

Hints

- Rewrite the numerator as a multiple of the denominator plus a remainder. - The constant outside the fraction determines the horizontal asymptote. - The numerator zero in the original form determines the x-intercept.

Solution

1. Rewrite the numerator as \(2x+7=2(x+3)+1\). Thus, \(f(x)=2+\frac{1}{x+3}\). 2. The vertical asymptote is \(x=-3\), and the horizontal asymptote is \(y=2\). 3. The x-intercept satisfies \(2x+7=0\), so \(x=-\frac{7}{2}\). 4. The form \(2+\frac{1}{x+3}\) displays the horizontal asymptote directly because the fractional term approaches \(0\). The original numerator-over-denominator form displays the x-intercept directly because it comes from the numerator zero.

Answer

a) \(f(x)=2+\frac{1}{x+3}\) b) Horizontal asymptote: \(y=2\); vertical asymptote: \(x=-3\); x-intercept: \(\left(-\frac{7}{2}, 0\right)\) c) The transformed form shows the horizontal asymptote most directly; the original form shows the x-intercept most directly.
Reciprocal function graphs and transformations 58
Consider \(f(x) = \frac{12}{x}\) and \(g(x) = \frac{24}{x}\), where \(x \neq 0\). a) Evaluate both functions for \(x \in \{1, 2, 3, 4, 6, 12\}\) and organize the results in a table. b) For the same positive input, which corresponding point is farther from the origin? Explain using the parameters. c) In which quadrants do the branches lie? Explain why the graphs never cross either coordinate axis.

Hints

- Compare the outputs when the denominator stays the same but the numerator doubles. - Determine the signs of the input and output in each branch. - A nonzero constant numerator prevents the function value from being \(0\). - Substituting \(x = 0\) would create division by zero.

Solution

1. Evaluate each function at the six given inputs. The outputs of \(g\) are twice the corresponding outputs of \(f\). 2. For every \(x > 0\), \(g(x) = 2f(x) > f(x)\). The points have the same positive \(x\)-coordinate, but the point on \(g\) has the larger \(y\)-coordinate, so it is farther from the origin. 3. Since both numerator parameters are positive, positive inputs give positive outputs and negative inputs give negative outputs. Thus, the branches lie in Quadrants I and III. 4. The graphs do not cross the \(y\)-axis because \(x = 0\) is excluded from the domain. They do not cross the \(x\)-axis because a fraction with a nonzero constant numerator cannot equal \(0\).

Answer

a) <table> <tr><td>\(x\)</td><td>\(1\)</td><td>\(2\)</td><td>\(3\)</td><td>\(4\)</td><td>\(6\)</td><td>\(12\)</td></tr> <tr><td>\(f(x)\)</td><td>\(12\)</td><td>\(6\)</td><td>\(4\)</td><td>\(3\)</td><td>\(2\)</td><td>\(1\)</td></tr> <tr><td>\(g(x)\)</td><td>\(24\)</td><td>\(12\)</td><td>\(8\)</td><td>\(6\)</td><td>\(4\)</td><td>\(2\)</td></tr> </table> b) For the same positive input, the point on \(g\) is farther from the origin because \(g(x) = 2f(x)\). c) The branches lie in Quadrants I and III. The graphs cannot cross the \(y\)-axis because \(x = 0\) is excluded, and they cannot cross the \(x\)-axis because their numerators are nonzero.
Reciprocal function graphs and transformations 59
Let \(f(x)=\frac{x-2}{x+1}\). a) Find the domain, x-intercept, vertical asymptote, and horizontal asymptote of \(f\). b) Rewrite the function in the form \(f(x)=a+\frac{b}{x+1}\). Find \(a\) and \(b\). c) Describe how to transform the graph of \(y=\frac{1}{x}\) to obtain the graph of \(f\).

Hints

- Find the value that makes the denominator zero. - Compare the degrees and leading coefficients to find the horizontal asymptote. - Rewrite the numerator using \(x+1\). - In the form \(a\frac{1}{x-h}+k\), identify the reflection, stretch, and translations.

Solution

1. The denominator is zero at \(x=-1\), so the domain is \(\mathbb{R}\setminus\{-1\}\). 2. The numerator is zero at \(x=2\), so the x-intercept is \((2, 0)\). 3. Since the denominator is zero and the numerator is nonzero at \(x=-1\), the vertical asymptote is \(x=-1\). The numerator and denominator have the same degree, so the horizontal asymptote is the ratio of the leading coefficients: \(y=1\). 4. Rewrite the numerator as \(x-2=(x+1)-3\): \(f(x)=\frac{x+1-3}{x+1}=1-\frac{3}{x+1}\). Thus, \(a=1\) and \(b=-3\). 5. Starting with \(y=\frac{1}{x}\), stretch vertically by a factor of \(3\), reflect across the x-axis, shift left \(1\) unit, and shift up \(1\) unit.

Answer

a) Domain: \(\mathbb{R}\setminus\{-1\}\); x-intercept: \((2, 0)\); vertical asymptote: \(x=-1\); horizontal asymptote: \(y=1\) b) \(f(x)=1-\frac{3}{x+1}\), so \(a=1\) and \(b=-3\). c) Stretch vertically by a factor of \(3\), reflect across the x-axis, shift left \(1\) unit, and shift up \(1\) unit.
Reciprocal function graphs and transformations 60
Consider the family \(f_a(x)=\frac{ax-3}{x-1}\), where \(a\in\mathbb{R}\setminus\{3\}\). a) Find the horizontal and vertical asymptotes. b) Show algebraically that for every allowed value of \(a\), the graph is symmetric about the intersection point \(S\) of its asymptotes.

Hints

- Find the denominator zero and compare leading coefficients. - Rewrite the function as a constant plus a reciprocal term. - Compare the function values at \(1+h\) and \(1-h\).

Solution

1. The denominator is zero at \(x=1\). Since \(a\neq 3\), the numerator at \(x=1\) is nonzero, so the vertical asymptote is \(x=1\). 2. The numerator and denominator have the same degree, so the horizontal asymptote is \(y=a\). Their intersection is \(S=(1, a)\). 3. Rewrite the function: \(f_a(x)=a+\frac{a-3}{x-1}\). 4. Let \(x=1+h\), where \(h\neq 0\). Then \(f_a(1+h)-a=\frac{a-3}{h}\), while \(f_a(1-h)-a=-\frac{a-3}{h}\). 5. Thus, points with x-coordinates equally spaced from \(1\) have y-values equally spaced on opposite sides of \(a\). Therefore, the graph is symmetric about \((1, a)\).

Answer

a) Vertical asymptote: \(x=1\); horizontal asymptote: \(y=a\) b) The graph is symmetric about \(S=(1, a)\).
Reciprocal function graphs and transformations 61
Let \(f(x)=\frac{6}{x+2}-1\). Its x-intercept \(N\), its y-intercept \(T\), and the origin \(O=(0,0)\) form a right triangle. a) Calculate the coordinates of \(N\) and \(T\). Show your work. b) Find the area of triangle \(NTO\).

Hints

- Substitute \(x=0\) to find the y-intercept. - Set the function equal to \(0\) to find the x-intercept. - The triangle's legs lie along the coordinate axes. - Use the area formula for a right triangle.

Solution

1. To find \(T\), substitute \(x=0\): \(f(0)=\frac{6}{2}-1=2\). Therefore, \(T=(0,2)\). 2. To find \(N\), set \(f(x)=0\): \(\frac{6}{x+2}-1=0\). Then \(\frac{6}{x+2}=1\), so \(x=4\). Therefore, \(N=(4,0)\). 3. The legs of the right triangle lie on the coordinate axes and have lengths \(4\) and \(2\). 4. Its area is \(A=\frac{1}{2}\cdot4\cdot2=4\) square units.

Answer

a) \(N=(4,0)\) and \(T=(0,2)\) b) \(4\) square units
Reciprocal function graphs and transformations 62
The solid graph \(g\) was obtained from the dashed graph \(f(x) = \frac{1}{x}\) by reflections and translations. Describe the transformations and determine the function rule for \(g\).
Figure for problem 533156

Hints

- Read the new asymptotes to determine the translations. - Compare the branch orientation with the parent function. - Use the form \(\frac{a}{x - h} + k\).

Solution

1. The solid graph has the vertical asymptote \(x = 3\) and the horizontal asymptote \(y = -1\). 2. These asymptotes indicate a translation \(3\) units to the right and \(1\) unit down. 3. Relative to the new asymptotes, the branch orientation is reversed from the parent function. This indicates a reflection across the \(x\)-axis before the translations. 4. Therefore, the function rule is \(g(x) = -\frac{1}{x - 3} - 1\).

Answer

Reflect the graph of \(f\) across the \(x\)-axis, then translate it \(3\) units right and \(1\) unit down. The function rule is \(g(x) = -\frac{1}{x - 3} - 1\).
Reciprocal function graphs and transformations 63
Use the displayed rational-function graph to answer the questions. a) Find the vertical and horizontal asymptotes. b) Find the y-intercept and x-intercept. c) Which rule describes the graph? I) \(f(x)=\frac{2x+4}{x-1}\) II) \(f(x)=\frac{x+2}{x-1}\) III) \(f(x)=\frac{2x-4}{x+1}\)
Figure for problem 533284

Hints

- Read the lines approached by the graph. - Read the axis crossings. - Check the asymptotes and intercepts of each candidate rule.

Solution

1. From the graph, the vertical asymptote is \(x=1\), and the horizontal asymptote is \(y=2\). 2. The graph crosses the y-axis at \((0, -4)\) and the x-axis at \((-2, 0)\). 3. Rule I has vertical asymptote \(x=1\), horizontal asymptote \(y=2\), x-intercept \((-2, 0)\), and y-intercept \((0, -4)\). Therefore, it matches every displayed feature. 4. Rule II has horizontal asymptote \(y=1\), and Rule III has vertical asymptote \(x=-1\), so neither matches.

Answer

a) Vertical asymptote: \(x=1\); horizontal asymptote: \(y=2\) b) Y-intercept: \((0, -4)\); x-intercept: \((-2, 0)\) c) I) \(f(x)=\frac{2x+4}{x-1}\)
Reciprocal function graphs and transformations 64
The graph of \(f(x) = \frac{-2}{x + 3} + 1\) is shown. a) Find the horizontal and vertical asymptotes. b) Describe the transformations that produce the graph of \(f\) from \(h(x) = \frac{1}{x}\). c) Find the x-intercept of \(f\).
Figure for problem 533317

Hints

- The vertical asymptote occurs where the denominator is zero. - The constant added outside the fraction determines the vertical shift. - Analyze the sign, scale factor, and translations one at a time. - Set the function equal to zero to find the x-intercept.

Solution

1. The denominator is zero at \(x = -3\), so the vertical asymptote is \(x = -3\). As \(|x|\) increases, \(\frac{-2}{x + 3}\) approaches \(0\), so the horizontal asymptote is \(y = 1\). 2. Starting from \(h(x) = \frac{1}{x}\), reflect across the x-axis, stretch vertically by a factor of \(2\), shift left \(3\) units, and shift up \(1\) unit. 3. Set \(f(x) = 0\): \(0 = \frac{-2}{x + 3} + 1\). Then \(\frac{2}{x + 3} = 1\), so \(x + 3 = 2\) and \(x = -1\).

Answer

a) Vertical asymptote: \(x = -3\); horizontal asymptote: \(y = 1\) b) Reflect across the x-axis, stretch vertically by \(2\), shift left \(3\), and shift up \(1\). c) The x-intercept is \((-1, 0)\).
Reciprocal function graphs and transformations 65
Let \(f(x)=\frac{1}{x}\). The graph and dashed asymptotes show two transformations, \(g\) and \(h\), of \(f\). Describe the transformations and determine the function rules for \(g\) and \(h\).
Figure for problem 534580

Hints

- Compare each graph’s vertical and horizontal asymptotes with those of \(\frac{1}{x}\). - Use the quadrants containing the branches to identify a reflection. - Substitute a point with integer coordinates to determine a scale factor.

Solution

1. For \(g\), the vertical asymptote moves from \(x=0\) to \(x=-2\), so the graph shifts left \(2\) units. The horizontal asymptote moves from \(y=0\) to \(y=1\), so the graph shifts up \(1\) unit. 2. Therefore, \(g(x)=\frac{1}{x+2}+1\). 3. For \(h\), both asymptotes remain unchanged. The branches move to Quadrants II and IV, so the graph is reflected across the x-axis. 4. The point \((1, -2)\) lies on \(h\), so the reflected graph is also stretched vertically by a factor of \(2\). Therefore, \(h(x)=-\frac{2}{x}\).

Answer

\(g\): shift left \(2\) units and up \(1\) unit; \(g(x)=\frac{1}{x+2}+1\) \(h\): reflect across the x-axis and stretch vertically by a factor of \(2\); \(h(x)=-\frac{2}{x}\)
Reciprocal function graphs and transformations 66
Let \(f(x) = \frac{1}{x - 4} + 2\). First reflect its graph across its own horizontal asymptote. Then translate the reflected graph \(3\) units left. Find the function rule for the resulting function \(g\), and state its asymptotes.

Hints

- Identify the horizontal asymptote before reflecting. - A reflection across the horizontal asymptote reverses the sign of the fraction term. - A translation left replaces \(x\) with \(x + d\). - Determine the new vertical asymptote from the final denominator.

Solution

1. The horizontal asymptote of \(f\) is \(y = 2\). 2. Reflecting across \(y = 2\) reverses the signed distance from that line. Therefore, the reciprocal term changes sign while the constant remains \(2\): \(r(x) = -\frac{1}{x - 4} + 2\). 3. Translating \(r\) \(3\) units left replaces \(x\) with \(x + 3\): \(g(x) = r(x + 3) = -\frac{1}{(x + 3) - 4} + 2 = -\frac{1}{x - 1} + 2\). 4. The denominator is zero at \(x = 1\), so the vertical asymptote is \(x = 1\). The horizontal asymptote remains \(y = 2\).

Answer

\(g(x) = -\frac{1}{x - 1} + 2\); vertical asymptote: \(x = 1\); horizontal asymptote: \(y = 2\)
Reciprocal function graphs and transformations 67
Consider the function \(f(x) = \frac{2}{x + 3} - 1\). Its graph is a translated hyperbola. Find the equations of the two lines of symmetry of the graph.

Hints

- First find the intersection of the asymptotes. - What slopes do the lines of symmetry of a rectangular hyperbola have? - Use point-slope form for a line through the center.

Solution

1. The vertical asymptote is \(x = -3\), and the horizontal asymptote is \(y = -1\). Their intersection is the center \((-3, -1)\). 2. The two lines of symmetry pass through the center and have slopes \(1\) and \(-1\). 3. For slope \(1\), use point-slope form: \(y + 1 = x + 3\), so \(y = x + 2\). 4. For slope \(-1\), \(y + 1 = -(x + 3)\), so \(y = -x - 4\).

Answer

The lines of symmetry are \(y = x + 2\) and \(y = -x - 4\).
Reciprocal function graphs and transformations 68
Consider \(f(x) = \frac{18}{x}\) and \(g(x) = \frac{36}{x}\). a) Evaluate both functions at \(x = 3\). b) For a fixed output \(y_0 > 0\), let \(x_f\) satisfy \(f(x_f) = y_0\) and let \(x_g\) satisfy \(g(x_g) = y_0\). Find \(\frac{x_g}{x_f}\). c) In Quadrant I, compare the graphs for equal positive inputs and for equal positive outputs. Which graph is farther from the corresponding coordinate axis in each comparison?

Hints

- Substitute \(x = 3\) into each function. - In part b), solve both equations for \(x\) before forming the ratio. - Compare outputs for equal inputs and inputs for equal outputs separately.

Solution

1. Evaluate at \(x = 3\): \(f(3) = \frac{18}{3} = 6\), and \(g(3) = \frac{36}{3} = 12\). 2. Solve each equation for the input: \(x_f = \frac{18}{y_0}\) and \(x_g = \frac{36}{y_0}\). 3. Therefore, \(\frac{x_g}{x_f} = \frac{36/y_0}{18/y_0} = 2\). 4. For the same positive input, \(g(x) = 2f(x)\), so the point on \(g\) is twice as far above the \(x\)-axis. 5. For the same positive output, \(x_g = 2x_f\), so the point on \(g\) is twice as far to the right of the \(y\)-axis. This is a stretch, not a translation.

Answer

a) \(f(3) = 6\) and \(g(3) = 12\) b) \(\frac{x_g}{x_f} = 2\) c) For equal positive inputs, the graph of \(g\) is farther from the \(x\)-axis. For equal positive outputs, it is farther from the \(y\)-axis.
Reciprocal function graphs and transformations 69
Consider the rational function \(f(x) = \frac{x + 3}{x - 1}\). 1) Rewrite the function in the form \(f(x) = \frac{k}{x - x_0} + y_0\). 2) Write the equations of the vertical and horizontal asymptotes. 3) Find the center of symmetry \(Z\) of the hyperbola. 4) Find the intersection points of the graph and the line of symmetry \(y = x\).

Hints

- Can the numerator be written as the denominator plus a constant? - Which input is excluded by the denominator? - What point is formed by the intersection of the asymptotes? - To find intersections with \(y = x\), set \(f(x) = x\).

Solution

1. Rewrite the numerator as \(x + 3 = (x - 1) + 4\): \(f(x) = \frac{(x - 1) + 4}{x - 1} = 1 + \frac{4}{x - 1}\). 2. Therefore, the vertical asymptote is \(x = 1\), and the horizontal asymptote is \(y = 1\). 3. Their intersection is the center of symmetry \(Z(1, 1)\). 4. Set \(f(x) = x\): \(\frac{x + 3}{x - 1} = x\). Then \(x + 3 = x(x - 1)\), so \(x^2 - 2x - 3 = 0\). Factoring gives \((x - 3)(x + 1) = 0\), so \(x = 3\) or \(x = -1\). The intersection points are \((3, 3)\) and \((-1, -1)\).

Answer

1) \(f(x) = \frac{4}{x - 1} + 1\) 2) Vertical asymptote: \(x = 1\); horizontal asymptote: \(y = 1\) 3) \(Z(1, 1)\) 4) \((3, 3)\) and \((-1, -1)\)

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