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End behavior and leading term analysis

Learning goals

  • Identifies the leading term of a polynomial.
  • Uses degree and leading coefficient to determine end behavior.
  • Matches algebraic end behavior with graph behavior.
  • Distinguishes end behavior from local behavior.

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End behavior and leading term analysis 1
Let \(g(x)=-0.5x^4+3x^2-1\). Describe the end behavior as \(x\to\infty\) and as \(x\to-\infty\).

Hints

- Identify the leading term. - Use the parity of the degree and the sign of the leading coefficient.

Solution

1. The leading term is \(-0.5x^4\), which controls the end behavior. 2. The degree is even, so both ends point in the same direction. 3. The leading coefficient is negative, so both ends point downward. Therefore, \(g(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\).

Answer

\(g(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\).
End behavior and leading term analysis 2
The displayed graph represents a fourth-degree polynomial function. Describe the end behavior as \(x\to\infty\) and as \(x\to-\infty\). What can you conclude about the leading coefficient? Justify your answer from the graph.
Figure for problem 533937

Hints

- Trace the graph far to the right and far to the left. - For an even-degree polynomial, the sign of the leading coefficient determines whether both ends rise or both fall.

Solution

1. The right end rises without bound, so \(f(x)\to\infty\) as \(x\to\infty\). 2. The left end also rises without bound, so \(f(x)\to\infty\) as \(x\to-\infty\). 3. A fourth-degree polynomial has even degree. Since both ends rise, its leading coefficient is positive.

Answer

As \(x\to\infty\), \(f(x)\to\infty\). As \(x\to-\infty\), \(f(x)\to\infty\). The leading coefficient is positive.
End behavior and leading term analysis 3
The graph of a polynomial function \(h\) is shown. Complete the end-behavior statements. As \(x \to \infty\), \(h(x) \to \square\). As \(x \to -\infty\), \(h(x) \to \square\). Then determine whether the degree must be even or odd.
Figure for problem 533938

Hints

- Read the direction of the graph at the far left and far right. - Opposite end directions indicate an odd degree.

Solution

1. The right end rises, so \(h(x) \to \infty\) as \(x \to \infty\). 2. The left end falls, so \(h(x) \to -\infty\) as \(x \to -\infty\). 3. Because the two ends move in opposite directions, the degree must be odd.

Answer

As \(x \to \infty\), \(h(x) \to \infty\). As \(x \to -\infty\), \(h(x) \to -\infty\). The degree is odd.
End behavior and leading term analysis 4
Find the leading term, degree, and leading coefficient of \(p(x)=4x-3x^5+2x^2\).

Hints

- Which term has the greatest exponent of \(x\)? - The leading coefficient includes the sign of that term.

Solution

1. The highest exponent is \(5\), so the leading term is \(-3x^5\). 2. The degree is \(5\), and the leading coefficient is \(-3\).

Answer

Leading term: \(-3x^5\); degree: \(5\); leading coefficient: \(-3\).
End behavior and leading term analysis 5
Two functions have rules \(f(x)=ax^2\) and \(g(x)=bx^2\), where \(a\) and \(b\) are nonzero constants. Their values are shown. <table><tr><th>\(x\)</th><th>\(-3\)</th><th>\(-2\)</th><th>\(2\)</th><th>\(3\)</th></tr><tr><td>\(f(x)\)</td><td>\(9\)</td><td>\(4\)</td><td>\(4\)</td><td>\(9\)</td></tr><tr><td>\(g(x)\)</td><td>\(-9\)</td><td>\(-4\)</td><td>\(-4\)</td><td>\(-9\)</td></tr></table> Which function has both graph ends rising, and which has both ends falling?

Hints

- What does the table tell you about the signs of the two coefficients? - For a positive or negative coefficient multiplying \(x^2\), what happens at large positive and negative inputs?

Solution

1. The table shows that \(f(2)=4\), so \(4a=4\) and \(a=1>0\). Its quadratic graph rises at both ends. 2. The table shows that \(g(2)=-4\), so \(4b=-4\) and \(b=-1<0\). Its quadratic graph falls at both ends.

Answer

Both ends of \(f\) rise; both ends of \(g\) fall.
End behavior and leading term analysis 6
As \(x\) moves farther from zero, do the two ends of the polynomial graph rise or fall?
Figure for problem 561758

Hints

- Look at the leftmost and rightmost parts rather than only the middle. - Compare the direction near each low point with the direction farther toward each edge.

Solution

1. On both the far left and far right of the displayed curve, the graph bends upward. 2. The local low points do not determine the direction of the ends. Both ends rise.

Answer

Both ends rise.
End behavior and leading term analysis 7
Analyze each power function for symmetry and end behavior. State whether the graph is symmetric about the y-axis or the origin, and describe what happens as \(x\to\infty\) and as \(x\to-\infty\). a) \(f(x)=-5x^8\) b) \(g(x)=0.4x^3\)

Hints

- Use the parity of the degree to determine symmetry. - Use the sign of the leading coefficient to determine whether the ends rise or fall. - Consider very large positive and negative inputs.

Solution

1. For \(f(x)=-5x^8\), the degree is even, so the graph is symmetric about the y-axis. The leading coefficient is negative, so both ends fall: \(f(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\). 2. For \(g(x)=0.4x^3\), the degree is odd, so the graph is symmetric about the origin. The leading coefficient is positive, so the left end falls and the right end rises: \(g(x)\to\infty\) as \(x\to\infty\) and \(g(x)\to-\infty\) as \(x\to-\infty\).

Answer

a) Symmetric about the y-axis; \(f(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\) b) Symmetric about the origin; \(g(x)\to\infty\) as \(x\to\infty\), and \(g(x)\to-\infty\) as \(x\to-\infty\)
End behavior and leading term analysis 8
Consider polynomial functions with \(f(x)\to+\infty\) as \(x\to\infty\) and as \(x\to-\infty\). a) Give an example with no real zeros. b) Give an example with exactly two real zeros. c) State the general conditions on the degree \(n\) and leading coefficient \(a_n\) that produce this end behavior.

Hints

- Start with an upward-opening quadratic. - Shift it vertically to change the number of x-intercepts. - Use the leading term to determine the direction of both ends.

Solution

1. One example with no real zeros is \(f(x)=x^2+1\). It is always at least \(1\), and both ends rise. 2. One example with exactly two real zeros is \(g(x)=x^2-4\). Its zeros are \(-2\) and \(2\), and both ends rise. 3. In general, the degree must be even so the two ends have the same direction, and the leading coefficient must be positive so both ends point upward.

Answer

a) One example is \(f(x)=x^2+1\). b) One example is \(g(x)=x^2-4\). c) \(n\) is even and \(a_n>0\).
End behavior and leading term analysis 9
Which of the following polynomial functions have the same end behavior as \(x \to \infty\) and as \(x \to -\infty\), meaning both ends rise or both ends fall? Justify your choices using the degree and leading coefficient. \(f(x) = -3x^4 + 2x^2 - 5\) \(g(x) = 0.2x^5 - x^3\) \(h(x) = x^6 + 4x^4 - 1\) \(k(x) = -x^7 + 10x^2\)

Hints

- Focus on the leading term of each polynomial. - Compare the end behavior of even and odd powers. - Identify the highest power of \(x\) in each expression. - The sign of the leading coefficient determines whether matching ends rise or fall, not whether the two ends match.

Solution

1. A polynomial has the same behavior on both ends when its degree is even. 2. Function \(f\) has degree 4 and a negative leading coefficient, so both ends fall. 3. Function \(g\) has degree 5, so its ends have opposite behavior. 4. Function \(h\) has degree 6 and a positive leading coefficient, so both ends rise. 5. Function \(k\) has degree 7, so its ends have opposite behavior.

Answer

\(f\) and \(h\)
End behavior and leading term analysis 10
Determine whether each function is a polynomial. For each polynomial, state its degree, leading coefficient, and end behavior as \(x \to \infty\) and \(x \to -\infty\). a) \(f(x) = -4x^6 + 2x^3 + 5\) b) \(g(x) = \frac{1}{3}(x^3 - 9x)\) c) \(h(x) = x^2 - 3\sqrt{x} + 1\)

Hints

- Check whether every exponent of \(x\) is a nonnegative integer. - Identify the leading term of each polynomial. - Use the parity of the degree and the sign of the leading coefficient.

Solution

1. Function \(f\) is a polynomial of degree 6 with leading coefficient \(-4\). Because the degree is even and the leading coefficient is negative, \(f(x) \to -\infty\) as \(x \to \pm\infty\). 2. Expand \(g\): \(g(x) = \frac{1}{3}x^3 - 3x\). It is a polynomial of degree 3 with leading coefficient \(\frac{1}{3}\). Thus, \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\). 3. Function \(h\) is not a polynomial because \(\sqrt{x} = x^{1/2}\) has a non-integer exponent.

Answer

a) Polynomial; degree \(6\); leading coefficient \(-4\); \(f(x) \to -\infty\) as \(x \to \pm\infty\) b) Polynomial; degree \(3\); leading coefficient \(\frac{1}{3}\); \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\) c) Not a polynomial because of \(\sqrt{x}\)
End behavior and leading term analysis 11
Describe the end behavior of each polynomial function as \(x \to \infty\) and as \(x \to -\infty\). a) \(f(x) = 4x^3 - x^4\) b) \(g(x) = \frac{1}{2}x(x^2 - 9)\) c) \(h(x) = -(x - 2)^2x\)

Hints

- Identify the leading term of each polynomial. - Use the degree and leading coefficient. - Compare even and odd powers for negative inputs. - For a product, determine the leading term without fully expanding when possible.

Solution

1. For \(f\), the leading term is \(-x^4\). The degree is even and the leading coefficient is negative, so \(f(x) \to -\infty\) as \(x \to \pm\infty\). 2. Expanding \(g\) gives \(g(x) = \frac{1}{2}x^3 - 4.5x\). The degree is odd and the leading coefficient is positive, so \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\). 3. Expanding \(h\) gives \(h(x) = -x^3 + 4x^2 - 4x\). The degree is odd and the leading coefficient is negative, so \(h(x) \to -\infty\) as \(x \to \infty\), and \(h(x) \to \infty\) as \(x \to -\infty\).

Answer

a) \(f(x) \to -\infty\) as \(x \to \pm\infty\) b) \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\) c) \(h(x) \to -\infty\) as \(x \to \infty\), and \(h(x) \to \infty\) as \(x \to -\infty\)
End behavior and leading term analysis 12
State the end behavior of each function as \(x \to \infty\) and as \(x \to -\infty\). a) \(p(x) = 0.2x^6 - 100x^3\) b) \(q(x) = (1 - x^2)(x^2 + 1)\) c) \(r(x) = x^3 - x^5 + 2\)

Hints

- The terms may not be written in descending powers. - Use algebraic identities to identify the leading term efficiently. - Compare the effect of even and odd exponents on large negative inputs.

Solution

1. For \(p\), the leading term is \(0.2x^6\). Its degree is even and its leading coefficient is positive, so \(p(x) \to \infty\) as \(x \to \pm\infty\). 2. Simplify \(q\): \(q(x) = 1 - x^4\). Its degree is even and its leading coefficient is negative, so \(q(x) \to -\infty\) as \(x \to \pm\infty\). 3. For \(r\), the leading term is \(-x^5\). Its degree is odd and its leading coefficient is negative, so \(r(x) \to -\infty\) as \(x \to \infty\), and \(r(x) \to \infty\) as \(x \to -\infty\).

Answer

a) \(p(x) \to \infty\) as \(x \to \pm\infty\) b) \(q(x) \to -\infty\) as \(x \to \pm\infty\) c) \(r(x) \to -\infty\) as \(x \to \infty\), and \(r(x) \to \infty\) as \(x \to -\infty\)
End behavior and leading term analysis 13
Analyze the end behavior of each polynomial function as \(x \to \infty\) and as \(x \to -\infty\). a) \(f(x) = -0.1x^4 + 5x - 1\) b) \(g(x) = \frac{2}{3}x^5 - 10x^2\)

Hints

- Identify the leading term of each polynomial. - Determine whether the leading term has even or odd degree. - Use the sign of the leading coefficient to decide whether each end rises or falls.

Solution

1. The leading term determines the end behavior of a polynomial function. 2. For \(f(x) = -0.1x^4 + 5x - 1\), the leading term is \(-0.1x^4\). Its degree is even and its coefficient is negative, so \(f(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). 3. For \(g(x) = \frac{2}{3}x^5 - 10x^2\), the leading term is \(\frac{2}{3}x^5\). Its degree is odd and its coefficient is positive, so \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\).

Answer

a) \(f(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\) b) \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\)
End behavior and leading term analysis 14
Match each polynomial function with its end behavior. Functions: 1. \(a(x) = 5x^3 - x\) 2. \(b(x) = -x^4 + 8x^2\) 3. \(c(x) = -2x^5 + 1\) 4. \(d(x) = 0.5x^2 + 3x\) End behavior: I. The function approaches \(\infty\) as \(x \to \infty\) and as \(x \to -\infty\). II. The function approaches \(-\infty\) as \(x \to \infty\) and as \(x \to -\infty\). III. The function approaches \(\infty\) as \(x \to \infty\) and approaches \(-\infty\) as \(x \to -\infty\). IV. The function approaches \(-\infty\) as \(x \to \infty\) and approaches \(\infty\) as \(x \to -\infty\).

Hints

- Identify the leading term of each polynomial. - Determine whether its degree is even or odd. - Determine whether its leading coefficient is positive or negative. - Use those two features to decide the direction of the left and right ends.

Solution

1. For \(a(x) = 5x^3 - x\), the leading term \(5x^3\) has odd degree and a positive coefficient. The right end rises and the left end falls, so the match is III. 2. For \(b(x) = -x^4 + 8x^2\), the leading term \(-x^4\) has even degree and a negative coefficient. Both ends fall, so the match is II. 3. For \(c(x) = -2x^5 + 1\), the leading term \(-2x^5\) has odd degree and a negative coefficient. The right end falls and the left end rises, so the match is IV. 4. For \(d(x) = 0.5x^2 + 3x\), the leading term \(0.5x^2\) has even degree and a positive coefficient. Both ends rise, so the match is I.

Answer

1. III 2. II 3. IV 4. I
End behavior and leading term analysis 15
Analyze the end behavior of each polynomial function. Match each function with the power function that has the same end behavior: \(f_1(x) = x^2\), \(f_2(x) = -x^2\), \(f_3(x) = x^3\), or \(f_4(x) = -x^3\). a) \(a(x) = -x^4 + 2x^2 + 5\) b) \(b(x) = (x + 1)(x - 2)(x + 3)\) c) \(c(x) = 4x^2 - x^5\) d) \(d(x) = \frac{1}{2}x^6 + 10x\)

Hints

- Identify the leading term of each polynomial. - Use whether the degree is even or odd to compare the two ends. - Use the sign of the leading coefficient to decide whether the right end rises or falls.

Solution

1. For \(a(x)\), the leading term is \(-x^4\). Its degree is even and its coefficient is negative, so both ends fall. This matches \(f_2(x) = -x^2\). 2. For \(b(x)\), the product of the leading terms is \(x^3\). Its degree is odd and its coefficient is positive, so the left end falls and the right end rises. This matches \(f_3(x) = x^3\). 3. For \(c(x)\), the leading term is \(-x^5\). Its degree is odd and its coefficient is negative, so the left end rises and the right end falls. This matches \(f_4(x) = -x^3\). 4. For \(d(x)\), the leading term is \(\frac{1}{2}x^6\). Its degree is even and its coefficient is positive, so both ends rise. This matches \(f_1(x) = x^2\).

Answer

a) \(f_2(x) = -x^2\) b) \(f_3(x) = x^3\) c) \(f_4(x) = -x^3\) d) \(f_1(x) = x^2\)
End behavior and leading term analysis 16
The leading term of a polynomial determines its end behavior. a) Describe the end behavior of \(p(x) = -x^3\) as \(x \to \infty\) and as \(x \to -\infty\). b) Determine whether \(g(x) = (2 - x)(x^2 + 4)\) has the same end behavior as \(p(x) = -x^3\). c) Which function has the same end behavior as \(h(x) = -3x^4 + 100x^3\): \(x^2\), \(-x^2\), \(x^3\), or \(-x^3\)? Justify your answer using the degree and leading coefficient.

Hints

- Focus on the leading term of each polynomial. - To find the leading term of a product, multiply the leading terms of the factors. - Compare the degree and sign of the leading coefficient with the four reference functions.

Solution

1. The function \(p(x) = -x^3\) has odd degree and a negative leading coefficient. Therefore, \(p(x) \to -\infty\) as \(x \to \infty\), and \(p(x) \to \infty\) as \(x \to -\infty\). 2. For \(g(x)\), the leading terms of the factors are \(-x\) and \(x^2\), so the leading term of the product is \(-x^3\). Therefore, \(g\) has the same end behavior as \(p\). 3. The leading term of \(h(x)\) is \(-3x^4\). Its degree is even and its coefficient is negative, so both ends fall. This matches the end behavior of \(-x^2\).

Answer

a) \(p(x) \to -\infty\) as \(x \to \infty\), and \(p(x) \to \infty\) as \(x \to -\infty\) b) Yes. The leading term of \(g\) is \(-x^3\). c) \(-x^2\)
End behavior and leading term analysis 17
Analyze the end behavior of \(f(x) = -2x^5 + 10x^3 - 4\) as \(x \to \infty\) and as \(x \to -\infty\). Justify your answer using the degree and leading coefficient.

Hints

- Identify the leading term. - Determine whether the degree is even or odd. - Use the sign of the leading coefficient to decide which end rises.

Solution

1. The leading term is \(-2x^5\). 2. The degree is \(5\), which is odd, and the leading coefficient is \(-2\), which is negative. 3. Therefore, the right end falls and the left end rises: \(f(x) \to -\infty\) as \(x \to \infty\), and \(f(x) \to \infty\) as \(x \to -\infty\).

Answer

\(f(x) \to -\infty\) as \(x \to \infty\), and \(f(x) \to \infty\) as \(x \to -\infty\)
End behavior and leading term analysis 18
The functions are \(g(x) = -x^4 + 3x^2\) and \(h(x) = -0.5x^6 + 10x^5\). Determine whether they have the same end behavior as \(x \to \infty\) and as \(x \to -\infty\). Justify your answer by comparing their degrees and leading coefficients.

Hints

- Identify the leading term of each polynomial. - Compare whether the two degrees are even or odd. - Decide whether the lower-degree terms affect end behavior.

Solution

1. The leading term of \(g\) is \(-x^4\). Its degree is even and its coefficient is negative, so \(g(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). 2. The leading term of \(h\) is \(-0.5x^6\). Its degree is even and its coefficient is negative, so \(h(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). 3. Therefore, the two functions have the same end behavior.

Answer

Yes. For both functions, the degree is even and the leading coefficient is negative, so the function values approach \(-\infty\) at both ends.
End behavior and leading term analysis 19
Determine the end behavior of each polynomial as \(x\to\infty\) and as \(x\to-\infty\). a) \(f(x)=-4x^3+12x-5\) b) \(g(x)=\frac{1}{4}x^4-2x^3+10x\) c) \(h(x)=500x^2-x^5\) d) \(k(x)=-(x^2-1)(x^2+2)\)

Hints

- Identify the leading term of each polynomial. - Use the parity of the degree to decide whether the two ends point in the same or opposite directions. - Use the sign of the leading coefficient to decide whether the right end rises or falls. - Expand part d) enough to identify its leading term.

Solution

1. The leading term of \(f\) is \(-4x^3\). Its degree is odd and its leading coefficient is negative, so \(f(x)\to-\infty\) as \(x\to\infty\) and \(f(x)\to\infty\) as \(x\to-\infty\). 2. The leading term of \(g\) is \(\frac{1}{4}x^4\). Its degree is even and its leading coefficient is positive, so both ends rise. 3. The leading term of \(h\) is \(-x^5\). Its degree is odd and its leading coefficient is negative, so the left end rises and the right end falls. 4. Expanding gives \(k(x)=-x^4-x^2+2\), whose leading term is \(-x^4\). Its degree is even and its leading coefficient is negative, so both ends fall.

Answer

a) \(f(x)\to-\infty\) as \(x\to\infty\), and \(f(x)\to\infty\) as \(x\to-\infty\). b) \(g(x)\to\infty\) as \(x\to\infty\) and as \(x\to-\infty\). c) \(h(x)\to-\infty\) as \(x\to\infty\), and \(h(x)\to\infty\) as \(x\to-\infty\). d) \(k(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\).
End behavior and leading term analysis 20
Match each function to panel a), b), or c). Explain your choices using symmetry and how fast the graphs grow. (1) \(y=x^3\) (2) \(y=x^4\) (3) \(y=x^6\)
Figure for problem 532293

Hints

- Compare the signs of the outputs on the left and right sides of each panel. - What symmetry would you expect from an odd power? From an even power? - Compare the two remaining functions at an input greater than \(1\).

Solution

1. The graph of \(y=x^3\) has odd degree and is symmetric about the origin. Panel c) has this behavior, so function (1) matches panel c). 2. The graphs of \(y=x^4\) and \(y=x^6\) are both symmetric about the y-axis. 3. For \(x>1\), \(x^6>x^4\), while for \(0<x<1\), \(x^6<x^4\). Panel a) has the steeper growth outside \([-1,1]\) and lies closer to the x-axis inside that interval, so it represents \(y=x^6\). Panel b) represents \(y=x^4\).

Answer

(1) Panel c) (2) Panel b) (3) Panel a)
End behavior and leading term analysis 21
Match each function rule with graph a, b, or c. Justify your choices using end behavior and symmetry. (I) \(p(x) = -0.5x^3 + 1.5x\) (II) \(q(x) = 0.25x^4 - 2x^2 + 1\) (III) \(r(x) = -0.1x^4 + 0.8x^2\)
Figure for problem 532379

Hints

- Identify the degree and sign of the leading coefficient. - Compare the direction of the two ends of each graph. - Determine whether each function has y-axis symmetry or origin symmetry. - Use the y-intercept to confirm the match.

Solution

1. Function (I) has odd degree and a negative leading coefficient, so its left end rises and its right end falls. It is symmetric about the origin. This matches graph a. 2. Function (II) has even degree and a positive leading coefficient, so both ends rise. It is symmetric about the y-axis and has y-intercept \(1\). This matches graph b. 3. Function (III) has even degree and a negative leading coefficient, so both ends fall. It is symmetric about the y-axis and passes through the origin. This matches graph c.

Answer

(I) Graph a (II) Graph b (III) Graph c
End behavior and leading term analysis 22
The graph shows a polynomial function \(f\). Its equation is not given. Assume the two ends continue in the directions shown, without any further turns. a) Describe what happens to \(f(x)\) as \(x\to\infty\) and as \(x\to-\infty\). b) Use the end behavior to explain: 1. why the degree of \(f\) must be odd; 2. why the leading coefficient of \(f\) must be negative.
Figure for problem 532422

Hints

- Read the direction of the graph at the far left and far right. - Describe how the function outputs change as the inputs get very large in each direction. - Compare the two end directions to the patterns for even and odd degrees. - Use the right-end direction to determine the sign of the leading coefficient.

Solution

1. On the left, the graph rises; on the right, it falls. Thus \(f(x)\to\infty\) as \(x\to-\infty\), and \(f(x)\to-\infty\) as \(x\to\infty\). 2. The two ends move in opposite directions, which is the end behavior of an odd-degree polynomial. 3. The right end falls as \(x\to\infty\), so the leading coefficient must be negative.

Answer

a) \(f(x)\to\infty\) as \(x\to-\infty\), and \(f(x)\to-\infty\) as \(x\to\infty\). b) 1. The ends move in opposite directions, so the degree is odd. 2. The right end falls, so the leading coefficient is negative.
End behavior and leading term analysis 23
The image shows two power functions, \(f(x)=ax^n\) and \(g(x)=bx^m\), with negative coefficients \(a,b<0\). 1. Which graph has an even exponent, and which has an odd exponent? Justify your answer. 2. Describe the behavior of both functions as \(x\to\infty\). 3. Give three possible function rules with different degrees that have the same symmetry and end behavior as graph \(f\).
Figure for problem 533466

Hints

- Compare y-axis symmetry with origin symmetry. - Use the negative leading coefficients to determine right-end behavior. - For graph \(f\), choose different positive even degrees and negative coefficients.

Solution

1. Graph \(f\) is symmetric about the y-axis, so its exponent is even. Graph \(g\) is symmetric about the origin, so its exponent is odd. 2. Because both coefficients are negative, both functions approach negative infinity as \(x\to\infty\). 3. Examples with even degree and negative leading coefficient include \(-x^2\), \(-0.5x^4\), and \(-2x^6\). Each is symmetric about the y-axis and falls on both ends.

Answer

1. Graph \(f\): even exponent; graph \(g\): odd exponent 2. Both functions approach \(-\infty\) as \(x\to\infty\). 3. Possible examples are \(-x^2\), \(-0.5x^4\), and \(-2x^6\).
End behavior and leading term analysis 24
Analyze graphs \(p\) and \(q\). For each graph, determine whether the polynomial has even or odd degree and whether its leading coefficient is positive or negative. Justify your answer using end behavior.
Figure for problem 533593

Hints

- Decide whether the two ends move in the same or opposite directions. - Use that comparison to determine whether the degree is even or odd. - Use the direction of the right end to determine the sign of the leading coefficient.

Solution

1. For graph \(p\), the left end falls and the right end rises. Since the ends move in opposite directions, the degree is odd. Since the right end rises, the leading coefficient is positive. 2. For graph \(q\), both ends fall. Since the ends move in the same direction, the degree is even. Since both ends fall, the leading coefficient is negative.

Answer

\(p\): odd degree; positive leading coefficient \(q\): even degree; negative leading coefficient
End behavior and leading term analysis 25
Match graphs \(f\), \(g\), and \(h\) with these function rules. Justify your choices using end behavior. 1. \(p_1(x) = 0.2x^4 - 2x^2 + 2\) 2. \(p_2(x) = -0.5x^3 + 3x\) 3. \(p_3(x) = 0.2x^5 - 2x^3\)
Figure for problem 533643

Hints

- Compare the direction of each graph's left and right ends. - Use whether the degree is even or odd. - Use the sign of the leading coefficient to determine which end rises.

Solution

1. Function \(p_1\) has even degree and a positive leading coefficient, so both ends rise. This matches graph \(f\). 2. Function \(p_2\) has odd degree and a negative leading coefficient, so the left end rises and the right end falls. This matches graph \(g\). 3. Function \(p_3\) has odd degree and a positive leading coefficient, so the left end falls and the right end rises. This matches graph \(h\).

Answer

1. \(p_1\): graph \(f\) 2. \(p_2\): graph \(g\) 3. \(p_3\): graph \(h\)
End behavior and leading term analysis 26
The graph shown represents a polynomial function \(f\). Describe the end behavior for very large positive and negative x-values. Write your results using arrow notation, such as \(x\to\infty\Rightarrow f(x)\to\square\). What does this behavior tell you about the sign of the leading coefficient \(a_n\)?
Figure for problem 533935

Hints

- Look at where the graph heads on the far left and far right. - Decide whether the y-values increase or decrease without bound on each end. - Use the direction of the right end to determine the sign of the leading coefficient.

Solution

1. On the right, the graph falls without bound. Thus, \(x\to\infty\Rightarrow f(x)\to-\infty\). 2. On the left, the graph rises without bound. Thus, \(x\to-\infty\Rightarrow f(x)\to\infty\). 3. The opposite end behaviors indicate an odd degree. Because the right end falls, the leading coefficient is negative, so \(a_n<0\).

Answer

\(x\to\infty\Rightarrow f(x)\to-\infty\) \(x\to-\infty\Rightarrow f(x)\to\infty\) The leading coefficient is negative: \(a_n<0\).
End behavior and leading term analysis 27
Consider the displayed graph of the polynomial function \(p\). Determine whether the degree is even or odd, and state the end behavior. Justify your answer.
Figure for problem 533936

Hints

- Compare whether the two ends move in the same or opposite directions. - Recall what matching end directions imply about the degree.

Solution

1. Both ends of the graph fall. 2. Because the two ends move in the same direction, the degree must be even. 3. The end behavior is \(p(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\).

Answer

The degree is even. Also, \(p(x)\to-\infty\) as \(x\to\infty\) and as \(x\to-\infty\).
End behavior and leading term analysis 28
Consider \(p(x)=2x^5-100x^3\) for \(x>0\). a) Find the positive input at which the two terms have equal absolute value. b) For inputs larger than that value, is \(p(x)\) positive or negative? Explain which term wins.

Hints

- Equal magnitudes lead to an equation involving both powers. - Because \(x\) is positive, dividing by a common positive power preserves the comparison. - Which power grows faster for large positive inputs?

Solution

1. For \(x>0\), equal magnitudes mean \(2x^5=100x^3\). Divide by \(2x^3>0\) to get \(x^2=50\), so \(x=5\sqrt{2}\). 2. For \(x>5\sqrt{2}\), \(2x^5>100x^3\). Thus, \(p(x)>0\); the fifth-degree term eventually dominates.

Answer

a) \(x=5\sqrt{2}\). b) Positive; \(2x^5\) is larger than \(100x^3\) for \(x>5\sqrt{2}\).
End behavior and leading term analysis 29
A polynomial has the values shown. <table><tr><th>\(x\)</th><th>\(-2\)</th><th>\(-1\)</th><th>\(1\)</th><th>\(2\)</th></tr><tr><td>\(f(x)\)</td><td>\(-8\)</td><td>\(-1\)</td><td>\(1\)</td><td>\(8\)</td></tr></table> Which graph, a) or b), matches the table? Describe its left and right end behavior.
Figure for problem 561760

Hints

- Look at the signs of the outputs for positive and negative inputs. - Compare the table with the shapes on each side of the y-axis. - Do both ends of each candidate graph point in the same direction?

Solution

1. The outputs change sign with the input, and their magnitudes fit a cubic relationship: \(f(x)=x^3\) is a matching rule. 2. Graph a) is the positive cubic; its left end falls and its right end rises. Graph b) has both ends falling.

Answer

Graph a). The left end falls, and the right end rises.
End behavior and leading term analysis 30
Two power functions, \(f(x)=ax^2\) and \(g(x)=bx^4\), both pass through \(P(2, -8)\). Their graphs are symmetric about the y-axis. 1. Find \(a\) and the function rule for \(f\). 2. Find \(b\) and the function rule for \(g\). 3. Compare the two coefficients. For \(x>2\), which function's output has the greater absolute value, and which grows faster in magnitude?

Hints

- Substitute the given point into each proposed function form. - Even exponents are consistent with y-axis symmetry. - Compare the degrees to determine which magnitude grows faster for large positive \(x\).

Solution

1. For \(f\), \(-8=a(2^2)=4a\), so \(a=-2\). Thus, \(f(x)=-2x^2\). 2. For \(g\), \(-8=b(2^4)=16b\), so \(b=-0.5\). Thus, \(g(x)=-0.5x^4\). 3. The coefficients are \(-2\) and \(-0.5\). For \(x>2\), \(\frac{|g(x)|}{|f(x)|}=\frac{0.5x^4}{2x^2}=\frac{x^2}{4}>1\). This ratio increases as \(x\) increases, so \(|g(x)|\) grows faster.

Answer

1. \(f(x)=-2x^2\) 2. \(g(x)=-0.5x^4\) 3. The coefficients are \(-2\) and \(-0.5\). For \(x>2\), \(|g(x)|>|f(x)|\), and \(|g(x)|\) grows faster.
End behavior and leading term analysis 31
Consider \(f(x)=x^3\) and \(g(x)=0.01x^5\). a) Find all x-values at which the functions have the same value. b) Compare the functions for very large positive values of \(x\). Which function eventually remains greater? Justify your answer.

Hints

- Factor out the greatest common power of \(x\). - How does the degree affect a polynomial's growth for large positive inputs? - Test a value greater than the largest intersection point.

Solution

1. Set the functions equal: \(x^3=0.01x^5\). 2. Factor: \(0.01x^5-x^3=x^3(0.01x^2-1)=0\). 3. Thus, \(x=0\) or \(0.01x^2=1\). The latter gives \(x^2=100\), so \(x=-10\) or \(x=10\). 4. The function \(g\) has the higher-degree leading term, so it grows faster as \(x\to\infty\). In fact, after the last intersection, \(g(x)>f(x)\) for every \(x>10\).

Answer

a) \(x=-10, 0, 10\) b) \(g(x)=0.01x^5\) eventually remains greater. For all \(x>10\), \(g(x)>f(x)\).
End behavior and leading term analysis 32
The nonzero coefficients of two polynomial functions are given. Write each function and describe its end behavior as \(x \to \infty\) and \(x \to -\infty\). a) For \(g\): \(a_4 = -2\), \(a_2 = 5\), and \(a_0 = -1\) b) For \(h\): \(a_3 = 4\) and \(a_1 = -2\)

Hints

- Identify the leading term of each polynomial. - Use whether the degree is even or odd. - Use the sign of the leading coefficient. - Compare with the end behavior of basic power functions such as \(x^2\), \(-x^2\), \(x^3\), and \(-x^3\).

Solution

1. The functions are \(g(x) = -2x^4 + 5x^2 - 1\) and \(h(x) = 4x^3 - 2x\). 2. Function \(g\) has even degree and a negative leading coefficient. Therefore, \(g(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). 3. Function \(h\) has odd degree and a positive leading coefficient. Therefore, \(h(x) \to \infty\) as \(x \to \infty\), and \(h(x) \to -\infty\) as \(x \to -\infty\).

Answer

a) \(g(x) = -2x^4 + 5x^2 - 1\); \(g(x) \to -\infty\) as \(x \to \pm\infty\) b) \(h(x) = 4x^3 - 2x\); \(h(x) \to \infty\) as \(x \to \infty\), and \(h(x) \to -\infty\) as \(x \to -\infty\)
End behavior and leading term analysis 33
A polynomial function \(p\) must satisfy \(p(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). Which equations meet this condition? 1) \(p_1(x) = -x^2(x^2 - 4)\) 2) \(p_2(x) = -(x - 2)^3\) 3) \(p_3(x) = -5x^6 + 100x^5\) 4) \(p_4(x) = (1 - x^2)x^2\) 5) \(p_5(x) = -x^4 - x^5\) Briefly state the required conditions on the degree and leading coefficient.

Hints

- Consider the sign of a large negative input raised to an even or odd power. - Expand only enough to identify the leading term. - The first written term is not always the leading term. - Determine which degree and leading-coefficient combination makes both ends fall.

Solution

1. Both ends fall when the polynomial has even degree and a negative leading coefficient. 2. For \(p_1\), the leading term is \(-x^4\). Its degree is even and its leading coefficient is negative, so it meets the condition. 3. For \(p_2\), the leading term is \(-x^3\). Its degree is odd, so it does not meet the condition. 4. For \(p_3\), the leading term is \(-5x^6\). Its degree is even and its leading coefficient is negative, so it meets the condition. 5. For \(p_4\), expanding gives \(x^2 - x^4\), whose leading term is \(-x^4\). It meets the condition. 6. For \(p_5\), the leading term is \(-x^5\). Its degree is odd, so it does not meet the condition.

Answer

1), 3), and 4). The degree must be even, and the leading coefficient must be negative.
End behavior and leading term analysis 34
A polynomial function \(f\) has this end behavior: \(f(x) \to -\infty\) as \(x \to \infty\), and \(f(x) \to \infty\) as \(x \to -\infty\). 1. What must be true about the degree and leading coefficient? 2. Which functions have this end behavior? Briefly justify each choice. \(p(x) = -0.5x^3 + 2x^2\) \(q(x) = x^4 - 10x^3\) \(r(x) = (2 - x)x^2\)

Hints

- Compare the end behavior of even and odd powers. - Determine how a negative leading coefficient reverses the parent power function. - Focus on the leading term of each expression.

Solution

1. Opposite end behavior requires an odd degree. Because the right end falls, the leading coefficient must be negative. 2. Function \(p\) has degree 3 and leading coefficient \(-0.5\), so it has the required behavior. 3. Function \(q\) has degree 4, so both ends have the same behavior. It does not qualify. 4. Expanding \(r\) gives \(r(x) = -x^3 + 2x^2\). It has degree 3 and leading coefficient \(-1\), so it qualifies.

Answer

1. The degree must be odd, and the leading coefficient must be negative. 2. \(p\) and \(r\)
End behavior and leading term analysis 35
Find one cubic polynomial function \(f\) that satisfies all three conditions. 1. \(f(x) \to \infty\) as \(x \to \infty\), and \(f(x) \to -\infty\) as \(x \to -\infty\). 2. The graph has y-intercept \(-3\). 3. The graph passes through \(P(1, 0)\).

Hints

- Determine the required sign of the leading coefficient for an odd-degree polynomial. - Use the y-intercept to determine the constant term. - Try a simple cubic containing only the cubic and constant terms. - Substitute the given point to determine the remaining coefficient.

Solution

1. A cubic with the stated end behavior must have a positive leading coefficient. 2. The y-intercept condition gives \(f(0) = -3\), so the constant term is \(-3\). 3. Choose the simple form \(f(x) = ax^3 - 3\), where \(a > 0\). 4. Use \(P(1, 0)\): \(0 = a(1)^3 - 3\), so \(a = 3\). 5. Therefore, one possible function is \(f(x) = 3x^3 - 3\).

Answer

One possible function is \(f(x) = 3x^3 - 3\).
End behavior and leading term analysis 36
Find one fourth-degree polynomial function \(f\) that satisfies all four conditions. 1. The graph is symmetric about the y-axis. 2. \(f(x) \to -\infty\) as \(x \to \pm\infty\). 3. \(f(0) = 2\). 4. \(f(2) = 0\).

Hints

- Y-axis symmetry restricts the powers that may appear. - Determine the required sign of the leading coefficient. - Use \(f(0)\) to find the constant term. - Substitute the zero and choose a convenient negative leading coefficient.

Solution

1. Y-axis symmetry allows the form \(f(x) = ax^4 + bx^2 + c\). 2. Both ends must fall, so the leading coefficient must satisfy \(a < 0\). 3. From \(f(0) = 2\), \(c = 2\). 4. From \(f(2) = 0\), \(16a + 4b + 2 = 0\). 5. Choose \(a = -1\). Then \(-16 + 4b + 2 = 0\), so \(b = 3.5\). 6. One possible function is \(f(x) = -x^4 + 3.5x^2 + 2\).

Answer

One possible function is \(f(x) = -x^4 + 3.5x^2 + 2\).
End behavior and leading term analysis 37
The functions are \(f(x) = 4x^4 - 2x^2\) and \(g(x) = kx^4 + x^3\), where \(k\) is real. Define \(h(x) = f(x) + g(x)\). a) Describe the end behavior of \(h\) when \(k = -4\). b) For which values of \(k\) does \(h(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\)? Justify your answer using the degree and leading coefficient.

Hints

- Combine like powers of \(x\) first. - Check what happens to the fourth-degree term when \(k = -4\). - Both ends fall when the leading term has even degree and a negative coefficient. - Solve the resulting inequality for \(k\).

Solution

1. Combine like terms: \(h(x) = (4 + k)x^4 + x^3 - 2x^2\). 2. When \(k = -4\), the fourth-degree terms cancel, so \(h(x) = x^3 - 2x^2\). Its degree is odd and its leading coefficient is positive. Therefore, \(h(x) \to \infty\) as \(x \to \infty\), and \(h(x) \to -\infty\) as \(x \to -\infty\). 3. For both ends to fall, the fourth-degree leading coefficient must be negative. Thus, \(4 + k < 0\). 4. Solving gives \(k < -4\).

Answer

a) \(h(x) \to \infty\) as \(x \to \infty\), and \(h(x) \to -\infty\) as \(x \to -\infty\) b) \(k < -4\)
End behavior and leading term analysis 38
Determine whether there is a real value of \(a\) such that the graph of \(f(x) = a(x + 2)(x - 1)(x - 3)\) passes through \(P(0, 12)\) and has the same end behavior as \(g(x) = 5x^3\).

Hints

- Substitute the coordinates of the given point into the function. - Determine the degree from the factors. - Identify the leading term of the polynomial. - Compare the degree and sign of the leading coefficient with those of \(g\).

Solution

1. Use the point \(P(0, 12)\): \(f(0) = a(2)(-1)(-3) = 6a\). 2. Solve \(6a = 12\) to get \(a = 2\). 3. With \(a = 2\), the leading term of \(f\) is \(2x^3\). It has odd degree and a positive leading coefficient. 4. The leading term of \(g\) is \(5x^3\), which also has odd degree and a positive leading coefficient. Therefore, both functions approach \(\infty\) as \(x \to \infty\) and approach \(-\infty\) as \(x \to -\infty\). 5. Thus, \(a = 2\) satisfies both conditions.

Answer

Yes. The value is \(a = 2\).
End behavior and leading term analysis 39
Determine whether there is a real value of \(k\) such that the graph of \(f(x) = k(x^2 + 2)(x - 4)^2\) passes through \(P(2, 24)\) and satisfies \(f(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\).

Hints

- Substitute the given point to determine \(k\). - Determine the total degree from the factors. - Decide what sign the leading coefficient must have for both ends to fall. - Compare that required sign with the value of \(k\) from the point condition.

Solution

1. Use the point \(P(2, 24)\): \(f(2) = k(2^2 + 2)(2 - 4)^2 = k(6)(4) = 24k\). 2. Solve \(24k = 24\) to get \(k = 1\). 3. The polynomial has degree \(4\), and with \(k = 1\), its leading term is \(x^4\). 4. An even-degree polynomial with a positive leading coefficient approaches \(\infty\) at both ends, not \(-\infty\). 5. Therefore, no real value of \(k\) satisfies both conditions.

Answer

No. The point condition requires \(k = 1\), but then \(f(x) \to \infty\) as \(x \to \pm\infty\).
End behavior and leading term analysis 40
Consider a polynomial function \(g\) with odd degree \(n\), such as \(n = 3\) or \(n = 5\). a) Describe the end behavior of \(g\) when its leading coefficient \(a_n\) is positive. b) Use end behavior to explain why every odd-degree polynomial function must have at least one real zero.

Hints

- Recall the end behavior of \(x^3\) and \(x^5\). - Imagine tracing the continuous graph from one end to the other. - Decide whether changing the sign of the leading coefficient affects the existence of an x-intercept.

Solution

1. When an odd-degree polynomial has a positive leading coefficient, \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\). 2. More generally, every odd-degree polynomial has opposite end behavior, whether its leading coefficient is positive or negative. 3. Polynomial functions are continuous. Therefore, the graph must pass from negative function values to positive function values and cross the x-axis at least once. 4. Each x-intercept represents a real zero, so every odd-degree polynomial has at least one real zero.

Answer

a) \(g(x) \to \infty\) as \(x \to \infty\), and \(g(x) \to -\infty\) as \(x \to -\infty\) b) An odd-degree polynomial has opposite end behavior and is continuous, so its graph must cross the x-axis at least once.
End behavior and leading term analysis 41
An artist designs two sculptures. Let \(x\) be the common edge or side length, measured in meters. The first sculpture is a solid cube with edge length \(x\). The second is a rectangular prism with a square base of side length \(x\) and a fixed height of \(4\,\text{m}\). a) Write a volume function for each solid, \(V_C\) for the cube and \(V_P\) for the rectangular prism. b) Find the positive value of \(x\) for which the sculptures have equal volumes. c) Find the common volume. d) Explain why the cube's volume will be greater for all sufficiently large values of \(x\).

Hints

- Use the volume formulas for a cube and a rectangular prism. - Equal volumes lead to an equation that can be factored. - Compare the degrees of the two volume functions for large \(x\).

Solution

1. The volume functions are \(V_C(x)=x^3\) and \(V_P(x)=4x^2\). 2. Set the volumes equal: \(x^3=4x^2\). 3. Factor: \(x^2(x-4)=0\). Since \(x>0\), \(x=4\,\text{m}\). 4. The common volume is \(4^3=64\,\text{m}^3\). 5. The cubic term \(x^3\) grows faster than the quadratic term \(4x^2\). In fact, \(x^3>4x^2\) for every \(x>4\).

Answer

a) \(V_C(x)=x^3\) and \(V_P(x)=4x^2\) b) \(x=4\,\text{m}\) c) \(64\,\text{m}^3\) d) The cubic function eventually exceeds the quadratic function; specifically, \(V_C(x)>V_P(x)\) for \(x>4\).
End behavior and leading term analysis 42
A polynomial \(f(x)=a_nx^n+a_{n-1}x^{n-1}+\cdots+a_0\) satisfies \(f(x)\to\infty\) as \(x\to-\infty\) and \(f(x)\to-\infty\) as \(x\to\infty\). a) Must the degree \(n\) be even or odd? Briefly explain. b) Must the leading coefficient \(a_n\) be positive or negative? c) Give one possible cubic polynomial with this end behavior and y-intercept \(5\). d) Reflect the graph of \(f\) across the x-axis to obtain \(g(x)=-f(x)\). Describe the end behavior of \(g\).

Hints

- Decide whether opposite end behavior occurs for an even or odd degree. - Use the right-end behavior to determine the sign of the leading coefficient. - The y-intercept is \(f(0)\). - Reflecting across the x-axis multiplies every function value by \(-1\).

Solution

1. The two ends move in opposite directions, so \(n\) must be odd. An even-degree polynomial has the same type of behavior on both ends. 2. The right end falls as \(x\to\infty\), so the leading coefficient must be negative: \(a_n<0\). 3. A cubic with a negative leading coefficient and constant term \(5\) is \(f(x)=-x^3+5\). Its constant term gives \(f(0)=5\). 4. Multiplying every output by \(-1\) reverses both end behaviors. Therefore, \(g(x)\to-\infty\) as \(x\to-\infty\), and \(g(x)\to\infty\) as \(x\to\infty\).

Answer

a) \(n\) must be odd. b) \(a_n<0\). c) One possible answer is \(f(x)=-x^3+5\). d) \(g(x)\to-\infty\) as \(x\to-\infty\), and \(g(x)\to\infty\) as \(x\to\infty\).
End behavior and leading term analysis 43
Consider the four power functions below. \(f_1(x)=1.5x^4\) \(f_2(x)=-0.5x^6\) \(f_3(x)=0.2x^5\) \(f_4(x)=-3x^3\) a) Match graphs I and II to two of the functions. Justify each match using symmetry and end behavior. b) For each unused function, describe its symmetry, end behavior, and range.
Figure for problem 532289

Hints

- Use the parity of the degree to identify symmetry. - Use the sign of the leading coefficient to determine the direction of the ends. - For the unused functions, determine whether outputs are restricted to one side of zero or cover all real numbers.

Solution

1. Graph I is symmetric about the y-axis and both ends fall. It must have even degree and a negative leading coefficient, so graph I represents \(f_2(x)=-0.5x^6\). 2. Graph II is symmetric about the origin and rises from left to right. It must have odd degree and a positive leading coefficient, so graph II represents \(f_3(x)=0.2x^5\). 3. For \(f_1(x)=1.5x^4\), the graph is symmetric about the y-axis and both ends rise. Its range is \([0, \infty)\). 4. For \(f_4(x)=-3x^3\), the graph is symmetric about the origin, rises on the left and falls on the right, and has range \(( -\infty, \infty)\).

Answer

a) Graph I: \(f_2(x)=-0.5x^6\); Graph II: \(f_3(x)=0.2x^5\) b) \(f_1\): even; both ends rise; range \([0, \infty)\). \(f_4\): odd; the left end rises and the right end falls; range \(( -\infty, \infty)\).
End behavior and leading term analysis 44
Four polynomial functions are given. 1. \(f(x) = 0.5x^3 - 2x\) 2. \(g(x) = -0.25x^4 + 2x^2\) 3. \(h(x) = 0.15x^4 - 1.5x^2 + 2\) 4. \(k(x) = -0.3x^3 + 1.5x\) Match graphs A, B, and C with their function rules. Justify each match using end behavior. Which function rule is not used?
Figure for problem 532326

Hints

- Identify the leading term of each function. - Use whether the degree is even or odd to compare the two ends. - Use the sign of the leading coefficient to determine whether the right end rises or falls. - Compare these conclusions with the left and right edges of each graph.

Solution

1. The leading term of \(f\) is \(0.5x^3\). The degree is odd and the leading coefficient is positive, so the left end falls and the right end rises. This matches graph B. 2. The leading term of \(g\) is \(-0.25x^4\). The degree is even and the leading coefficient is negative, so both ends fall. This matches graph A. 3. The leading term of \(h\) is \(0.15x^4\). The degree is even and the leading coefficient is positive, so both ends rise. This matches graph C. 4. The leading term of \(k\) is \(-0.3x^3\). The degree is odd and the leading coefficient is negative, so the left end rises and the right end falls. None of the displayed graphs has this end behavior, so \(k\) is not used.

Answer

A: \(g(x)=-0.25x^4+2x^2\); B: \(f(x)=0.5x^3-2x\); C: \(h(x)=0.15x^4-1.5x^2+2\); not used: \(k(x)=-0.3x^3+1.5x\)
End behavior and leading term analysis 45
Four polynomial functions are given: \(p(x) = x^3 - 3x\) \(q(x) = -x^3 + x\) \(r(x) = -x^4 + 2x^2\) \(s(x) = x^4 - 2x^2\) The figure shows the graphs of two of these functions. a) Match graphs 1 and 2 with their function rules. b) Justify each match using end behavior and symmetry.
Figure for problem 532327

Hints

- Determine which function rules are even and which are odd. - Compare the direction of each graph's left and right ends. - Use the sign of the leading coefficient to choose between functions with the same symmetry.

Solution

1. Graph 1 has its left end falling and its right end rising, so it must have odd degree and a positive leading coefficient. It is also symmetric about the origin. Among the choices, only \(p(x) = x^3 - 3x\) has these properties. 2. Graph 2 has both ends falling, so it must have even degree and a negative leading coefficient. It is also symmetric about the y-axis. Among the choices, only \(r(x) = -x^4 + 2x^2\) has these properties.

Answer

a) Graph 1: \(p(x) = x^3 - 3x\); Graph 2: \(r(x) = -x^4 + 2x^2\) b) Graph 1 has odd-degree positive-leading-coefficient end behavior and origin symmetry. Graph 2 has even-degree negative-leading-coefficient end behavior and y-axis symmetry.
End behavior and leading term analysis 46
Match each polynomial function with panel a), b), c), or d). Use end behavior, symmetry, or intercepts to explain your choices. a) \(g_1(x)=x^3-3x^2+2\) b) \(g_2(x)=0.5x^3-2x\) c) \(g_3(x)=0.2x^4-x^2-1\) d) \(g_4(x)=-0.25x^4+2x^2\)
Figure for problem 532329

Hints

- Begin with the degree and sign of the leading coefficient. - Group the graphs by whether their ends rise or fall. - Check whether each function is even, odd, or neither. - Use the y-intercept to distinguish functions with the same end behavior.

Solution

1. Both \(g_1\) and \(g_2\) have odd degree and a positive leading coefficient, so their left ends fall and their right ends rise. They match panels a) and c). 2. The even-degree polynomial \(g_3\) has a positive leading coefficient, so both ends rise. It matches panel d). 3. The even-degree polynomial \(g_4\) has a negative leading coefficient, so both ends fall. It matches panel b). 4. Since \(g_1(0)=2\), \(g_1\) matches panel c). Since \(g_2(0)=0\), \(g_2\) matches panel a). The origin symmetry of \(g_2\) confirms this match.

Answer

a) \(g_1\): panel c) b) \(g_2\): panel a) c) \(g_3\): panel d) d) \(g_4\): panel b)
End behavior and leading term analysis 47
Let \(f(x) = -x^4 + 2x^2\). The figure shows graphs A and B, which are graphs of two other polynomial functions. a) Use end behavior and the y-intercept to explain why neither graph A nor graph B can represent \(f\). b) Find all real zeros of \(f\) algebraically.
Figure for problem 532331

Hints

- Evaluate \(f(0)\) and compare it with each graph's y-intercept. - Use the leading term to determine the end behavior of \(f\). - Factor out the greatest common factor to solve \(f(x) = 0\). - Apply the zero-product property.

Solution

1. The y-intercept of \(f\) is \(f(0) = 0\), so its graph must pass through \((0, 0)\). Graph A has y-intercept \(2\), so graph A cannot represent \(f\). 2. The leading term of \(f\) is \(-x^4\). Its degree is even and its coefficient is negative, so \(f(x) \to -\infty\) as \(x \to \infty\) and as \(x \to -\infty\). Graph B rises at both ends, so graph B cannot represent \(f\). 3. Set the function equal to zero: \(-x^4 + 2x^2 = 0\). 4. Factor: \(-x^2(x^2 - 2) = 0\). 5. Therefore, \(x = 0\) or \(x^2 = 2\), which gives \(x = -\sqrt{2}\), \(x = 0\), and \(x = \sqrt{2}\).

Answer

a) Graph A has the wrong y-intercept, and graph B has the wrong end behavior. b) \(x = -\sqrt{2}, 0, \sqrt{2}\)
End behavior and leading term analysis 48
Let \(f(x) = x^4 - 4x^2\). The figure shows graphs A and B, which are graphs of two other polynomial functions. a) Explain why neither graph A nor graph B can represent \(f\). Use end behavior, zeros, and the y-intercept. b) Determine the symmetry of the graph of \(f\). Then use the multiplicities of the zeros to state where the graph crosses the x-axis and where it only touches the x-axis.
Figure for problem 532334

Hints

- Use the leading term to determine the end behavior of \(f\). - Evaluate \(f(0)\) and compare the y-intercepts. - Check \(f(-x)\) to determine symmetry. - Factor \(f\) and use the multiplicity of each zero.

Solution

1. The leading term of \(f\) is \(x^4\), so \(f(x) \to \infty\) as \(x \to \infty\) and as \(x \to -\infty\). Graph A falls at both ends, so it cannot represent \(f\). 2. Since \(f(0) = 0\), the graph of \(f\) passes through the origin. Graph B has y-intercept \(4\). It also has zeros at \(x = \pm 1\) and \(x = \pm 2\), which do not match the zeros of \(f\). Therefore, graph B cannot represent \(f\). 3. Because \(f(-x) = f(x)\), the graph is symmetric about the y-axis. 4. Factor the function: \(f(x) = x^2(x - 2)(x + 2)\). 5. The zero \(x = 0\) has multiplicity \(2\), so the graph touches the x-axis there. The zeros \(x = -2\) and \(x = 2\) have multiplicity \(1\), so the graph crosses the x-axis at those points.

Answer

a) Graph A has the wrong end behavior. Graph B has the wrong y-intercept and zeros. b) The graph is symmetric about the y-axis. It touches the x-axis at \(x = 0\) and crosses at \(x = -2\) and \(x = 2\).
End behavior and leading term analysis 49
Three polynomial functions are given: \(p(x) = -0.5x^3 + 2x\) \(q(x) = 0.25x^4 - 2x^2 + 1\) \(r(x) = (x - 1)^3 - 1\) Match each function with graph a, b, or c. Justify each match using end behavior and another characteristic such as symmetry, an intercept, or a notable point.
Figure for problem 532336

Hints

- Begin with the degree and sign of the leading coefficient. - Compare the direction of the two ends of each graph. - Check for y-axis symmetry or origin symmetry. - Evaluate the y-intercept or identify a translated cubic's central point.

Solution

1. The function \(p\) has odd degree and a negative leading coefficient, so its left end rises and its right end falls. It is also symmetric about the origin. Therefore, \(p\) matches graph a. 2. The function \(q\) has even degree and a positive leading coefficient, so both ends rise. It is symmetric about the y-axis and has y-intercept \(q(0) = 1\). Therefore, \(q\) matches graph b. 3. The function \(r\) has odd degree and a positive leading coefficient, so its left end falls and its right end rises. It is a translation of \(y = x^3\) with central point \((1, -1)\). Therefore, \(r\) matches graph c.

Answer

\(p\): graph a; \(q\): graph b; \(r\): graph c
End behavior and leading term analysis 50
The figure shows graphs a and b, along with four possible function rules: 1) \(f(x) = 0.25x^3 - x\) 2) \(g(x) = -0.2x^4 + 1.2x^2\) 3) \(h(x) = -0.25x^3 + x\) 4) \(k(x) = 0.2x^4 - 1.2x^2\) Match graphs a and b with their function rules. Justify each choice using end behavior and another characteristic of the graph.
Figure for problem 532338

Hints

- Compare the left and right ends of each graph. - Use the degree and sign of each leading coefficient. - Check zeros or the y-intercept to confirm each match.

Solution

1. Graph a has its left end falling and its right end rising, so it must have odd degree and a positive leading coefficient. Only function 1 has this end behavior. 2. Function 1 factors as \(f(x) = 0.25x(x - 2)(x + 2)\), so its zeros are \(x = -2, 0, 2\), which agree with graph a. 3. Graph b falls at both ends, so it must have even degree and a negative leading coefficient. Only function 2 has this end behavior. 4. Function 2 factors as \(g(x) = -0.2x^2(x^2 - 6)\). The zero at \(x = 0\) has multiplicity \(2\), so the graph touches the x-axis at the origin, as graph b does.

Answer

Graph a: 1) \(f(x)=0.25x^3-x\); Graph b: 2) \(g(x)=-0.2x^4+1.2x^2\)
End behavior and leading term analysis 51
Match each polynomial function with panel a), b), c), or d). Explain each match using the graph's ends, symmetry, zeros, or turning points. 1) \(p_1(x) = x^3 - 3x\) 2) \(p_2(x) = -x^3 + 3x^2\) 3) \(p_3(x) = -0.25x^4 + 2x^2 - 2\) 4) \(p_4(x) = 0.5(x + 1)^2(x - 2)\)
Figure for problem 532345

Hints

- Begin with the direction of the two ends of each graph. - Check for y-axis symmetry or origin symmetry. - Compare y-intercepts. - Use zeros and their multiplicities to confirm the matches.

Solution

1. Graph c is symmetric about the y-axis and falls at both ends. This matches \(p_3\), which has even degree and a negative leading coefficient. 2. Graph b has its left end rising and its right end falling. This matches \(p_2\), which has odd degree and a negative leading coefficient. Its double zero at \(x = 0\) and simple zero at \(x = 3\) confirm the match. 3. Graphs a and d both have odd-degree positive-leading-coefficient end behavior. 4. Graph a is symmetric about the origin and has zeros at \(x = 0\) and \(x = \pm\sqrt{3}\), so it matches \(p_1\). 5. Graph d has y-intercept \(-1\), a double zero at \(x = -1\), and a simple zero at \(x = 2\), so it matches \(p_4\).

Answer

1) \(p_1\): a 2) \(p_2\): b 3) \(p_3\): c 4) \(p_4\): d
End behavior and leading term analysis 52
Four polynomial function rules are given: (1) \(f_1(x) = x^3 - 3x\) (2) \(f_2(x) = -x^3 + 3x\) (3) \(f_3(x) = x^4 - 3x^2\) (4) \(f_4(x) = -x^4 + 3x^2\) a) Match graphs A, B, and C with their function rules. One rule will not be used. b) Justify each match using end behavior and symmetry.
Figure for problem 532374

Hints

- Compare whether the two ends move in the same or opposite directions. - Determine whether each graph has y-axis symmetry or origin symmetry. - Use the sign of the leading coefficient to decide which end behavior applies. - Identify the one unused rule by its unmatched end behavior.

Solution

1. Graph A is symmetric about the origin, with its left end falling and its right end rising. This matches function (1), which has odd degree and a positive leading coefficient. 2. Graph B is symmetric about the y-axis and falls at both ends. This matches function (4), which has even degree and a negative leading coefficient. 3. Graph C is symmetric about the origin, with its left end rising and its right end falling. This matches function (2), which has odd degree and a negative leading coefficient. 4. Function (3) is not used because its even degree and positive leading coefficient would make both ends rise.

Answer

a) A: (1); B: (4); C: (2); not used: (3) b) A and C have origin symmetry and opposite odd-degree end behavior. B has y-axis symmetry and both ends fall.
End behavior and leading term analysis 53
The displayed graph represents a polynomial function. Give three different mathematical reasons why it cannot be the graph of \(f(x) = -0.5x^4 + 2x^2\). You may use end behavior, symmetry, function values, or behavior at zeros.
Figure for problem 532377

Hints

- Compare the left and right ends of the displayed graph with the leading term of \(f\). - Determine whether \(f\) is even, odd, or neither. - Factor \(f\) and examine the multiplicity of the zero at \(x = 0\). - Compare the graph and the function at a clearly readable integer x-value.

Solution

1. End behavior: The leading term of \(f\) is \(-0.5x^4\), so both ends of its graph fall. The displayed graph has its left end falling and its right end rising. 2. Symmetry: The function \(f\) is even because it contains only even powers, so its graph must be symmetric about the y-axis. The displayed graph is symmetric about the origin instead. 3. Behavior at the origin: Since \(f(x) = x^2(2 - 0.5x^2)\), \(x = 0\) is a zero of multiplicity \(2\). The graph of \(f\) must touch the x-axis at the origin, but the displayed graph crosses there. 4. Function value: \(f(2) = 0\), but the displayed graph passes through \((2, -2)\). 5. Any three of these contradictions are sufficient.

Answer

Possible reasons include: the end behavior is different; \(f\) has y-axis symmetry while the displayed graph has origin symmetry; \(f\) touches the x-axis at \(x = 0\) while the displayed graph crosses it; and \(f(2) = 0\) while the displayed graph has value \(-2\) at \(x = 2\). Any three are sufficient.
End behavior and leading term analysis 54
Three polynomial functions are given: \(f(x) = \frac{1}{4}x^3 - x\) \(g(x) = -\frac{1}{8}x^4 + x^2 - 1\) \(h(x) = \frac{1}{8}x^4 - x^2 + 2\) The graphs are labeled a, b, and c. Match each graph with its function rule and justify your choices using end behavior, the y-intercept, or symmetry.
Figure for problem 532443

Hints

- Compare the degree and sign of each leading coefficient. - Use the y-intercept to distinguish graphs with similar shapes. - Check whether each function has y-axis symmetry or origin symmetry. - Look for zeros where a graph touches rather than crosses the x-axis.

Solution

1. The function \(f\) has odd degree and a positive leading coefficient, so its left end falls and its right end rises. It is also symmetric about the origin and passes through \((0, 0)\). This matches graph b. 2. The function \(g\) has even degree and a negative leading coefficient, so both ends fall. It has y-intercept \(g(0) = -1\). This matches graph a. 3. The function \(h\) has even degree and a positive leading coefficient, so both ends rise. It has y-intercept \(h(0) = 2\), and \(h(x) = \frac{1}{8}(x - 2)^2(x + 2)^2\), so it touches the x-axis at \(x = -2\) and \(x = 2\). This matches graph c.

Answer

a: \(g(x) = -\frac{1}{8}x^4 + x^2 - 1\); b: \(f(x) = \frac{1}{4}x^3 - x\); c: \(h(x) = \frac{1}{8}x^4 - x^2 + 2\)
End behavior and leading term analysis 55
Emma is viewing the graph of \(f(x)=-0.01x^4+0.5x^2+2\). She claims, “Because the graph keeps rising toward the right edge, \(f(x)\) will keep rising as \(x\) gets larger.” Evaluate her claim. Describe the actual end behavior as \(x\to\infty\) and explain why the displayed graph is misleading.
Figure for problem 532455

Hints

- Identify the leading term of the polynomial. - Determine its sign for very large positive inputs. - Check a positive input outside the displayed window. - Could the graph turn after the visible interval ends?

Solution

1. The leading term is \(-0.01x^4\). For very large positive \(x\), this negative fourth-power term dominates, so \(f(x)\to-\infty\) as \(x\to\infty\). Emma’s claim is false. 2. Rewrite the function as \(f(x)=-0.01(x^2-25)^2+8.25\). This shows local maxima at \(x=-5\) and \(x=5\). 3. The graphing window ends exactly at those maxima. For \(x>5\), the graph turns downward, but that behavior is outside the displayed window. For example, \(f(10)=-48\).

Answer

Emma’s claim is false. \(f(x)\to-\infty\) as \(x\to\infty\). The graphing window ends at the local maximum \(x=5\), hiding the decrease for \(x>5\).
End behavior and leading term analysis 56
Match graphs 1 and 2 with two of the following function rules. Justify each choice, including a comparison of intercepts. \(f(x) = 0.5x^4 - 2\) \(g(x) = -x^4 + 2\) \(h(x) = -x^5 + x\) \(i(x) = x^5 - x\)
Figure for problem 533601

Hints

- Compare the y-intercepts by substituting \(x = 0\). - Determine whether each graph has y-axis symmetry or origin symmetry. - Compare the direction of the left and right ends.

Solution

1. Graph 1 is symmetric about the y-axis and rises at both ends, so it must have even degree and a positive leading coefficient. Its y-intercept is \(-2\). These features match \(f(x) = 0.5x^4 - 2\). 2. Graph 2 is symmetric about the origin, with its left end rising and its right end falling. It has zeros at \(x = -1, 0, 1\). These features match \(h(x) = -x^5 + x = -x(x - 1)(x + 1)(x^2 + 1)\).

Answer

Graph 1: \(f(x) = 0.5x^4 - 2\); Graph 2: \(h(x) = -x^5 + x\)
End behavior and leading term analysis 57
Let \(f(x) = -x^3 + x^2 + 2x\). a) Explain why neither graph A nor graph B can represent \(f\). Use zeros and end behavior. b) Describe the key features and overall shape of the graph of \(f\).
Figure for problem 533616

Hints

- Factor the polynomial to find its zeros. - Use the degree and leading coefficient to determine end behavior. - Compare these features with each displayed graph.

Solution

1. Factor the function: \(f(x) = -x(x^2 - x - 2) = -x(x - 2)(x + 1)\). The zeros are \(x = -1, 0, 2\). 2. The degree is \(3\) and the leading coefficient is negative. Therefore, \(f(x) \to \infty\) as \(x \to -\infty\), and \(f(x) \to -\infty\) as \(x \to \infty\). 3. Graph A has zeros at \(x = -2, 0, 1\), so its zeros do not match those of \(f\). 4. Graph B has the correct zeros, but its left end falls and its right end rises, which is the opposite of the end behavior of \(f\). 5. The graph comes from the upper left, crosses the x-axis at \(x = -1\), \(x = 0\), and \(x = 2\), and continues toward the lower right.

Answer

a) Graph A has the wrong zeros. Graph B has the correct zeros but the wrong end behavior. b) The graph crosses the x-axis at \((-1, 0)\), \((0, 0)\), and \((2, 0)\), with its left end rising and its right end falling.
End behavior and leading term analysis 58
Consider \(f(x) = 0.5x^4 - 2x^2\). a) Explain why neither graph A nor graph B can represent \(f\). Use symmetry, zeros, and end behavior. b) Describe the key features and overall shape of the graph of \(f\).
Figure for problem 533617

Hints

- Use the exponents to determine symmetry. - Factor the polynomial and identify each zero's multiplicity. - Use the leading term to determine the end behavior.

Solution

1. The function contains only even powers, so its graph is symmetric about the y-axis. 2. Factor: \(f(x) = 0.5x^2(x - 2)(x + 2)\). The zero \(x = 0\) has multiplicity \(2\), and \(x = -2\) and \(x = 2\) are simple zeros. 3. The degree is \(4\) and the leading coefficient is positive, so both ends rise. 4. Graph A has four simple zeros at \(x = \pm 1\) and \(x = \pm 2\), and it does not have a zero at the origin. Therefore, it cannot represent \(f\). 5. Graph B has the correct zeros and touches at the origin, but both ends fall. Therefore, it cannot represent \(f\). 6. The graph is W-shaped and symmetric about the y-axis. It crosses at \(x = -2\) and \(x = 2\), touches at \(x = 0\), and rises at both ends.

Answer

a) Graph A has the wrong zeros. Graph B has the correct zeros but the wrong end behavior. b) The graph is symmetric about the y-axis, crosses at \((-2, 0)\) and \((2, 0)\), touches at \((0, 0)\), and rises at both ends.
End behavior and leading term analysis 59
Match panels a), b), and c) with three of the function rules. One rule will not be used. Explain using end behavior and zeros. (1) \(p_1(x) = 0.5x^3 - 2x\) (2) \(p_2(x) = -x^2 + 4\) (3) \(p_3(x) = x^4 - 4x^2\) (4) \(p_4(x) = -0.5x^3 + 2x\)
Figure for problem 533779

Hints

- Compare the left and right ends of each graph. - Identify where each graph crosses or touches the x-axis. - Use a simple function value when needed to confirm a match. - Compare the degree with the overall graph shape.

Solution

1. Panel a) has odd-degree positive-leading-coefficient end behavior and zeros at \(x=-2,0,2\). It matches rule (1), since \(0.5x^3-2x=0.5x(x-2)(x+2)\). 2. Panel b) is a downward-opening parabola with vertex \((0,4)\) and zeros at \(x=\pm2\). It matches rule (2). 3. Panel c) has even-degree positive-leading-coefficient end behavior. It has a double zero at \(x=0\) and simple zeros at \(x=\pm2\). It matches rule (3), since \(x^4-4x^2=x^2(x-2)(x+2)\). 4. Rule (4) is not used because its left end rises and its right end falls.

Answer

a): rule (1) b): rule (2) c): rule (3) Not used: rule (4)
End behavior and leading term analysis 60
Consider the displayed graph and the function \(g(x) = x^4 - 4x^2 + 3\). Give three different mathematical reasons, such as symmetry, intercepts, or end behavior, that prove the displayed graph cannot represent \(g\).
Figure for problem 533785

Hints

- Determine whether \(g\) is even or odd. - Evaluate \(g(0)\). - Use the degree and leading coefficient to determine the end behavior. - Compare each algebraic feature with the displayed graph.

Solution

1. Symmetry: The function \(g\) contains only even powers, so it is even and its graph must be symmetric about the y-axis. The displayed graph is not symmetric about the y-axis. 2. Y-intercept: \(g(0) = 3\), so the graph of \(g\) must cross the y-axis at \((0, 3)\). The displayed graph crosses at \((0, 0)\). 3. End behavior: The leading term of \(g\) is \(x^4\), so \(g(x) \to \infty\) as \(x \to -\infty\) and as \(x \to \infty\). The displayed graph falls to the left and rises to the right.

Answer

1. \(g\) is symmetric about the y-axis, but the displayed graph is not. 2. The y-intercept of \(g\) is \((0, 3)\), but the displayed graph has y-intercept \((0, 0)\). 3. Both ends of the graph of \(g\) rise, but the displayed graph falls to the left and rises to the right.
End behavior and leading term analysis 61
Let \(h(x) = -0.5x^4 + 2x^2 - 1\). Explain three properties that prove the displayed graph cannot represent \(h\).
Figure for problem 533786

Hints

- Use the sign of the leading coefficient to determine end behavior. - Evaluate \(h(0)\). - Can you group the terms into an equivalent equation that looks easier to solve?

Solution

1. End behavior: The leading term is \(-0.5x^4\), so both ends of the graph of \(h\) must fall. The displayed graph rises at both ends. 2. Y-intercept: \(h(0) = -1\), but the displayed graph has y-intercept \(2\). 3. Zeros: Set \(-0.5x^4 + 2x^2 - 1 = 0\). Treating the equation as quadratic in \(x^2\) gives \(x^4-4x^2+2=0\), so \(x^2=2\pm\sqrt{2}\). Therefore, \(h\) has four real zeros: \(x=\pm\sqrt{2-\sqrt{2}}\) and \(x=\pm\sqrt{2+\sqrt{2}}\). The displayed graph has no x-intercepts.

Answer

The graph has the wrong end behavior, the wrong y-intercept, and the wrong number of real zeros.
End behavior and leading term analysis 62
The function \(f\) is defined by \(f(x) = \frac{1}{2}x^4 - 3x^2 + \frac{5}{2}\). a) Find all zeros of \(f\). b) Describe the end behavior of \(f\). Check your results using the graph.
Figure for problem 533787

Hints

- The equation for part a contains only even powers of \(x\). What simpler polynomial structure does that suggest? - For the end behavior, focus on the degree and sign of the leading coefficient. - Check whether the x-intercepts and the direction of both ends of the graph agree with your calculations.

Solution

1. Set \(f(x)=0\). Since the equation contains only \(x^4\) and \(x^2\), view it as a quadratic equation in \(x^2\): \(\frac{1}{2}x^4-3x^2+\frac{5}{2}=0\). 2. Multiply by \(2\): \(x^4-6x^2+5=0\). Factoring gives \((x^2-1)(x^2-5)=0\). 3. Thus \(x^2=1\) or \(x^2=5\), so the zeros are \(x=\pm1\) and \(x=\pm\sqrt{5}\). 4. The leading term is \(\frac{1}{2}x^4\). Its degree is even and its coefficient is positive, so \(f(x)\to\infty\) as \(x\to\infty\) and as \(x\to-\infty\). 5. The graph shows four x-intercepts near \(-\sqrt{5}\), \(-1\), \(1\), and \(\sqrt{5}\), and both ends rise.

Answer

a) The zeros are \(x=-\sqrt{5}\), \(x=-1\), \(x=1\), and \(x=\sqrt{5}\). b) \(f(x)\to\infty\) as \(x\to\pm\infty\).
End behavior and leading term analysis 63
Let \(f(x) = x^4 - 2x^2 + 1\). Give three different arguments that prove the displayed graph cannot represent \(f\).
Figure for problem 533789

Hints

- Determine the symmetry from the exponents. - Factor the function and identify the zeros and their multiplicities. - Use the squared form to determine whether the function can be negative. - Compare these properties with the displayed graph.

Solution

1. Symmetry: The function \(f\) contains only even powers, so its graph must be symmetric about the y-axis. The displayed graph is not symmetric about the y-axis. 2. Zeros and multiplicity: \(f(x) = (x^2 - 1)^2 = (x - 1)^2(x + 1)^2\). Therefore, the only zeros are \(x = -1\) and \(x = 1\), each with multiplicity \(2\), so the graph must touch the x-axis at those points. The displayed graph crosses the x-axis at four simple zeros: \(x = -2, -1, 1, 3\). 3. Sign of the function: Because \(f(x) = (x^2 - 1)^2\), \(f(x) \ge 0\) for every real \(x\). The displayed graph has portions below the x-axis.

Answer

The displayed graph has the wrong symmetry, the wrong zeros and multiplicities, and negative function values even though \(f(x) \ge 0\) for all real \(x\).
End behavior and leading term analysis 64
Match each function to the correct graph. Use symmetry and end behavior to justify your choices. \(g_1(x) = x^4 - 4x^2\) \(g_2(x) = x^3 - 4x\) \(g_3(x) = -x^3 + 4x\) \(g_4(x) = x^2 - 4\)
Figure for problem 533812

Hints

- Identify which functions contain only even powers and which contain only odd powers. - Use the degree to distinguish the parabola from the quartic graph. - Use the sign of the leading coefficient to distinguish the two cubic graphs.

Solution

1. The functions \(g_1\) and \(g_4\) contain only even powers, so both graphs are symmetric about the y-axis. The function \(g_1\) is quartic, which matches graph a, while \(g_4\) is an upward-opening parabola, which matches graph d. 2. The functions \(g_2\) and \(g_3\) contain only odd powers, so both graphs are symmetric about the origin. 3. The leading coefficient of \(g_2\) is positive, so its graph falls to the left and rises to the right. This matches graph c. 4. The leading coefficient of \(g_3\) is negative, so its graph rises to the left and falls to the right. This matches graph b.

Answer

\(a \to g_1\); \(b \to g_3\); \(c \to g_2\); \(d \to g_4\)
End behavior and leading term analysis 65
Graphs \(a\), \(b\), and \(c\) represent three cubic polynomial functions. Match each graph with its function rule and justify your choices. 1. \(f(x) = x^3 - 3x + 2\) 2. \(g(x) = -x^3 + 3x + 2\) 3. \(h(x) = 0.5x^3 - 1.5x + 1\)
Figure for problem 533978

Hints

- Compare the end behavior of the three graphs. - Evaluate each function at \(x = 0\). - Check a visible zero to confirm the match. - Compare the relative steepness of graphs with the same end behavior.

Solution

1. Functions \(f\) and \(h\) have positive leading coefficients, so their left ends fall and their right ends rise. These match graphs \(a\) and \(c\). 2. Function \(g\) has a negative leading coefficient, so its left end rises and its right end falls. This matches graph \(b\). 3. Compare y-intercepts: \(f(0) = 2\), so \(f\) matches graph \(a\). Also, \(h(0) = 1\), so \(h\) matches graph \(c\). 4. The zero at \(x = 1\) for both \(f\) and \(h\) confirms the two matches.

Answer

\(a\): \(f(x) = x^3 - 3x + 2\); \(b\): \(g(x) = -x^3 + 3x + 2\); \(c\): \(h(x) = 0.5x^3 - 1.5x + 1\)
End behavior and leading term analysis 66
Let \(g(x)=\frac{1}{100}x^4-2x^2+50\). Two viewing windows show the same graph. a) Describe the graph's apparent shape in Window 1 and Window 2. b) Explain from the formula why Window 1 is unsuitable for judging the graph's end behavior.
Figure for problem 534002

Hints

- Compare the sizes of the terms for small \(|x|\). - Identify the term that dominates for large \(|x|\). - Compare the scales of the two windows. - Use the leading term to determine end behavior.

Solution

1. In Window 1, where \(-2\le x\le2\), the term \(-2x^2+50\) dominates because \(\frac{1}{100}x^4\) is very small. The graph appears to be a downward-opening parabola. 2. In Window 2, the positive quartic term becomes dominant for larger \(|x|\), and the graph shows the W-shaped behavior of a positive-leading-coefficient quartic. 3. Window 1 can falsely suggest that the graph continues downward. In fact, the leading term \(\frac{1}{100}x^4\) determines the end behavior, so \(g(x)\to\infty\) as \(x\to\pm\infty\).

Answer

a) Window 1 looks like a downward-opening parabola; Window 2 shows a W-shaped quartic. b) The narrow window hides the eventual dominance of \(\frac{1}{100}x^4\). The actual end behavior is \(g(x)\to\infty\) as \(x\to\pm\infty\).
End behavior and leading term analysis 67
A maze game uses two ways to search an \(n\times n\) map, where \(n\) is a positive integer. A route search takes \(R(n)=2n^3+4n^2\) operations, while a tile search takes \(S(n)=10n^2+4n\) operations. a) Compare the operation counts when \(n=3\) and \(n=4\). b) For which positive integers \(n\) does the route search use more operations? Explain how the highest-degree terms affect the comparison for large \(n\).

Hints

- Begin by calculating the two counts for the given grid sizes. - To compare the models for any positive \(n\), look at the sign of their difference. - Once you find the positive point where the difference changes sign, remember that \(n\) must be an integer.

Solution

1. At \(n=3\), \(R(3)=54+36=90\) and \(S(3)=90+12=102\). At \(n=4\), \(R(4)=128+64=192\) and \(S(4)=160+16=176\). 2. Subtract: \(R(n)-S(n)=2n(n^2-3n-2)\). For positive \(n\), the sign depends on \(n^2-3n-2\). 3. Its positive zero is \(\frac{3+\sqrt{17}}{2}\), between \(3\) and \(4\). Hence \(R(n)>S(n)\) exactly for integers \(n\ge4\). The cubic leading term of \(R\) eventually outweighs the quadratic leading term of \(S\).

Answer

a) At \(n=3\): \(R=90\), \(S=102\). At \(n=4\): \(R=192\), \(S=176\). b) All positive integers \(n\ge4\). The cubic leading term eventually dominates the quadratic terms.
End behavior and leading term analysis 68
For which values of \(b \in \mathbb{R}\) and \(n \in \mathbb{N}\) does the polynomial \(f(x) = bx^n - 10x^6\) satisfy \(f(x) \to \infty\) as \(x \to \infty\) and as \(x \to -\infty\)? Justify your answer.

Hints

- Identify which term is the leading term. - Both ends rise only for an even degree with a positive leading coefficient. - Consider separately the cases \(n < 6\), \(n = 6\), and \(n > 6\). - Watch for cancellation when \(n = 6\).

Solution

1. Both ends rise when the leading term has even degree and a positive coefficient. 2. If \(n < 6\), the leading term is \(-10x^6\), so both ends fall. No values of \(b\) work. 3. If \(n = 6\), then \(f(x) = (b - 10)x^6\). The coefficient must be positive, so \(b > 10\). 4. If \(n > 6\), the leading term is \(bx^n\), provided \(b \neq 0\). Both ends rise exactly when \(n\) is even and \(b > 0\). 5. Therefore, the conditions are \(n = 6\) with \(b > 10\), or an even integer \(n > 6\) with \(b > 0\).

Answer

\(n = 6\) and \(b > 10\), or \(n \in \{8, 10, 12, \ldots\}\) and \(b > 0\)
End behavior and leading term analysis 69
Determine whether there is a fourth-degree polynomial function with a triple zero at \(x = -1\), a simple zero at \(x = 2\), passing through \((1, 16)\), and having the same end behavior as \(g(x) = -x^2\) as \(x \to \pm\infty\). Justify your conclusion.

Hints

- Build a factored expression from the zeros and their multiplicities. - Use the given point to determine the leading constant. - End behavior depends on the degree and the sign of the leading coefficient. - Compare the left- and right-end behavior with that of \(-x^2\).

Solution

1. The zeros and multiplicities require the form \(f(x) = a(x + 1)^3(x - 2)\). 2. Use the point \((1, 16)\): \(16 = a(1 + 1)^3(1 - 2) = a(8)(-1)\). Thus, \(a = -2\). 3. The function \(f(x) = -2(x + 1)^3(x - 2)\) has degree \(3 + 1 = 4\) and leading coefficient \(-2\). 4. A polynomial of even degree with a negative leading coefficient approaches \(-\infty\) on both ends. Therefore, \(f(x) \to -\infty\) as \(x \to \pm\infty\), matching the end behavior of \(g(x) = -x^2\). 5. Such a function does exist.

Answer

Yes. One such function is \(f(x) = -2(x + 1)^3(x - 2)\). Its degree is even and its leading coefficient is negative, so \(f(x) \to -\infty\) as \(x \to \pm\infty\).
End behavior and leading term analysis 70
Polynomial functions of odd degree have a special property related to their zeros. a) Use end behavior to explain why every odd-degree polynomial function must have at least one real zero. b) Let \(g(x) = (x^2 + 4)(x - 5)^2(x + 1)\). Determine the degree of \(g\), all of its real zeros, and the multiplicity of each real zero.

Hints

- Compare the two ends of the graph of an odd-degree polynomial. - Use the fact that polynomial functions are continuous. - Add the degrees of the factors to find the total degree. - Set each factor equal to zero and keep only real solutions. - Use each factor's exponent to determine multiplicity.

Solution

1. An odd-degree polynomial has opposite end behavior: one end approaches \(\infty\) and the other approaches \(-\infty\). 2. Polynomial functions are continuous. Therefore, as the graph moves from negative function values to positive function values, it must cross the x-axis at least once. Thus, every odd-degree polynomial has at least one real zero. 3. For \(g\), add the degrees of the factors: \(2 + 2 + 1 = 5\). Therefore, \(g\) has degree \(5\). 4. The factor \(x^2 + 4\) has no real zeros because \(x^2 + 4 > 0\) for every real \(x\). 5. The factor \((x - 5)^2\) gives the zero \(x = 5\) with multiplicity \(2\). 6. The factor \(x + 1\) gives the zero \(x = -1\) with multiplicity \(1\).

Answer

a) Because an odd-degree polynomial has opposite end behavior and is continuous, its graph must cross the x-axis at least once. b) Degree: \(5\); real zeros: \(x = 5\) with multiplicity \(2\), and \(x = -1\) with multiplicity \(1\)

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