Graph and analyze each function. Describe the domain, range, intercepts, end behavior, continuity, and where the function is increasing or decreasing. 1. f (x) = 0.25x 3 Evaluate the function for several x-values in its domain. x f(x) 1.5 0.07 1 0.25 0.5 2 0 0.5 2 1 0.25 1.5 0.07 Use these points to construct a graph. Since the power is negative, the function will be undefined at x = 0, and D = (, 0) (0, ). All values of y are included in the graph except 0, so R = (, 0) (0, ). The graph never intersects either axis, so there are no x- and y-intercepts. The y-values approach zero as x approaches negative or positive infinity, so and. The graph has an infinite discontinuity at x = 0. As you read the graph from left to right, it is going up from negative infinity to 0, and again going up from 0 to positive infinity, so the graph is increasing on (, 0) (0, ). esolutions Manual - Powered by Cognero Page 1
3. Solve each equation. x = 12 or x = 5 Since the each side of the equation was raised to a power, check the solutions in the original equation. x = 12 x = 5 One solution checks and the other solution does not. Therefore, the solution is x = 5. 5. 2 + = x The equation has no real solutions. esolutions Manual - Powered by Cognero Page 2
7. x 4 5x 3 14x 2 = 0 Factor. x 2 (x 2 5x 14) = 0 x 2 (x 7)(x + 2) = 0. The solutions are 0, 7, and 2. Describe the end behavior of the graph of each polynomial function using limits. Explain your reasoning using the leading term test. 9. f (x) = 5x 4 3x 3 7x 2 + 11x 8 The degree is even and the leading coefficient is positive. State the number of possible real zeros and turning points of each function. Then find all of the real zeros by factoring. 11. f (x) = 4x 3 + 8x 2 60x The degree of f (x) is 3, so it will have at most three real zeros and two turning points. So, the zeros are 5, 0, and 3. esolutions Manual - Powered by Cognero Page 3
13. MULTIPLE CHOICE Which function has 3 turning points? A f (x) = x 4 4 B f (x) = x 4 11x 3 C f (x) = x 3 + 9x 2 + 20x D f (x) = x 4 5x 2 + 4 In order for a function to have 3 turning points, the function has to have a degree of at least 4. This eliminates choice C. Use a graphing calculator to graph the remaining functions. A B D The correct answer is D. esolutions Manual - Powered by Cognero Page 4
For each function, (a) apply the leading term test, (b) find the zeros and state the multiplicity of any repeated zeros, (c) find a few additional points, and then (d) graph the function. 15. f (x) = x(x 1)(x + 3) a. The degree is 3, and the leading coefficient is 1. Because the degree is odd and the leading coefficient is positive, b. The zeros are 0, 1, 3. c. Sample answer: Evaluate the function for a few x-values in its domain. x f(x) 2 6 1 4 2 10 3 36 d. Evaluate the function for several x-values in its domain. x f(x) 5 60 4 20 3 0 0 0 1 0 4 84 5 160 Use these points to construct a graph. esolutions Manual - Powered by Cognero Page 5
Use the Factor Theorem to determine if the binomials given are factors of f (x). Use the binomials that are factors to write a factored form of f (x). 17. f (x) = x 3 3x 2 13x + 15; (x + 3) Use synthetic division to test the factor (x + 3). Because the remainder when the polynomial is divided by (x + 3) is 0, (x + 3) is a factor of f (x). Because (x + 3) is a factor of f (x), we can use the final quotient to write a factored form of f (x) as f (x) = (x + 3)(x 2 6x + 5). Factoring the quadratic expression yields f (x) = (x + 3)(x 1)(x 5). esolutions Manual - Powered by Cognero Page 6
19. WEATHER The table shows the average high temperature in Bay Town each month. a. Make a scatter plot for the data. b. Use a graphing calculator to model the data using a polynomial function with a degree of 3. Use x = 1 for January and round each coefficient to the nearest thousandth. c. Use the model to predict the average high temperature for the following January. Let x = 13. a. Create a scatter plot for the data. b. Use the cubic regression function on the graphing calculator. f(x) = 0.071x 3 + 0.415x 2 + 5.909x + 54.646 c. Find f (x) for x = 13. Graph the regression equation using a graphing calculator. Use the value function from the CALC menu on the calculator to find f (13). The average high temperature for the following January is 44.9. esolutions Manual - Powered by Cognero Page 7
Write a polynomial function of least degree with real coefficients in standard form that has the given zeros. 21. 5, 5, 1 i Because 1 i is a zero and the polynomial is to have real coefficients, you know that 1 + i must also be a zero. Using the Linear Factorization Theorem and the zeros 5, 5, 1 i, and 1 + i, write f (x) as follows. f(x) = a[x (5)][x ( 5)][x (1 i)][x (1 + i)] Let a = 1. Then write the function in standard form. Therefore, a function of least degree that has 5, 5, 1 i, and 1 + i as zeros is f (x) = x 4 2x 3 23x 2 + 50x 50 or any nonzero multiple of f (x). Divide using synthetic division. 23. f (x) = (x 3 7x 2 + 13) (x 2) Because x 2, c = 2. Set up the synthetic division as follows. Then follow the synthetic division procedure. The quotient is. esolutions Manual - Powered by Cognero Page 8
Determine any asymptotes and intercepts. Then graph the function and state its domain. 25. The function is undefined at b(x) = 0, so D = {x x 5, x }. There are vertical asymptotes at x = 5. There is a horizontal asymptote at y = 2, the ratio of the leading coefficients of the numerator and denominator, because the degrees of the polynomials are equal. The x-intercept is 3, the zero of the numerator. The y-intercept is because. Graph the asymptotes and intercepts. Then find and plot points. 26. f (x) = f(x) can be written as f (x) =. The function is undefined at b(x) = 0, so D = {x x 4, x }. There are vertical asymptotes at x = 4. Since the degree of the numerator is one larger than the degree of the denominator, the graph will have an oblique asymptote. Perform synthetic division to find the equation for the oblique asymptote. Because x 4, c = 4. Set up the synthetic division as follows. Then follow the synthetic division procedure. The equation for the oblique asymptote is y = x + 5. The x-intercepts are 2 and 3, the zeros of the numerator. The y-intercept is because. Graph the asymptotes and intercepts. Then find and plot points. esolutions Manual - Powered by Cognero Page 9
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