Section 2.2 Polynomial Functions of Higher Degree.

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Slide 1 Section 2.2 Polynomial Functions of Higher Degree Slide 2 What you should learn How to use transformations to sketch graphs of polynomial functions How to use the Leading Coefficient Test to determine the end behavior of graphs of polynomial functions How to use zeros of polynomial functions as sketching aids How to use the Intermediate Value theorem to help locate zeros of polynomial functions Slide 3 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 3 Polynomial Function A polynomial function is a function of the form where n is a nonnegative integer and each a i (i = 0, , n) is a real number. The polynomial function has a leading coefficient a n and degree n. Examples: Find the leading coefficient and degree of each polynomial function. Polynomial FunctionLeading Coefficient Degree -2 5 1 3 14 0 Slide 4 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 4 Graphs of Polynomial Functions Graphs of polynomial functions are continuous. That is, they have no breaks, holes, or gaps. Polynomial functions are also smooth with rounded turns. Graphs with points or cusps are not graphs of polynomial functions. x y x y continuousnot continuouscontinuous smoothnot smooth polynomialnot polynomial x y f (x) = x 3 5x 2 + 4x + 4 Slide 5 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 5 Power Functions Polynomial functions of the form f (x) = x n, n 1 are called power functions. If n is even, their graphs resemble the graph of f (x) = x 2. If n is odd, their graphs resemble the graph of f (x) = x 3. x y x y f (x) = x 2 f (x) = x 5 f (x) = x 4 f (x) = x 3 Slide 6 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 6 Example: Graph of f(x) = (x + 2) 4 Example: Sketch the graph of f (x) = (x + 2) 4. This is a shift of the graph of y = x 4 two units to the left. This, in turn, is the reflection of the graph of y = x 4 in the x-axis. x y y = x 4 y = x 4 f (x) = (x + 2) 4 Slide 7 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 7 Leading Coefficient Test As x grows positively or negatively without bound, the value f (x) of the polynomial function f (x) = a n x n + a n 1 x n 1 + + a 1 x + a 0 (a n 0) grows positively or negatively without bound depending upon the sign of the leading coefficient a n and whether the degree n is odd or even. x y x y n odd n even a n positive a n negative Slide 8 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 8 Example: Right-Hand and Left-Hand Behavior Example: Describe the right-hand and left-hand behaviour for the graph of f(x) = 2x 3 + 5x 2 x + 1. As, and as, Negative-2Leading Coefficient Odd3Degree x y f (x) = 2x 3 + 5x 2 x + 1 Slide 9 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 9 Zeros of a Function A real number a is a zero of a function y = f (x) if and only if f (a) = 0. A turning point of a graph of a function is a point at which the graph changes from increasing to decreasing or vice versa. A polynomial function of degree n has at most n 1 turning points and at most n zeros. Real Zeros of Polynomial Functions If y = f (x) is a polynomial function and a is a real number then the following statements are equivalent. 1. a is a zero of f. 2. a is a solution of the polynomial equation f (x) = 0. 3. x a is a factor of the polynomial f (x). 4. (a, 0) is an x-intercept of the graph of y = f (x). Slide 10 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 10 Example: Real Zeros Example: Find all the real zeros and turning points of the graph of f (x) = x 4 x 3 2x 2. Factor completely: f (x) = x 4 x 3 2x 2 = x 2 (x + 1)(x 2). The real zeros are x = 1, x = 0, and x = 2. These correspond to the x-intercepts (1, 0), (0, 0) and (2, 0). The graph shows that there are three turning points. Since the degree is four, this is the maximum number possible. y x f (x) = x 4 x 3 2x 2 Turning point Slide 11 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 11 Repeated Zeros Example: Determine the multiplicity of the zeros of f (x) = (x 2) 3 (x +1) 4. Zero Multiplicity Behavior 2 1 3 4 odd even crosses x-axis at (2, 0) touches x-axis at (1, 0) Repeated Zeros If k is the largest integer for which (x a) k is a factor of f (x) and k > 1, then a is a repeated zero of multiplicity k. 1. If k is odd the graph of f (x) crosses the x-axis at (a, 0). 2. If k is even the graph of f (x) touches, but does not cross through, the x-axis at (a, 0). x y Slide 12 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 12 Example: Graph of f(x) = 4x 2 x 4 Example: Sketch the graph of f (x) = 4x 2 x 4. 1. Write the polynomial function in standard form: f (x) = x 4 + 4x 2 The leading coefficient is negative and the degree is even. 2. Find the zeros of the polynomial by factoring. f (x) = x 4 + 4x 2 = x 2 (x 2 4) = x 2 (x + 2)(x 2) Zeros: x = 2, 2 multiplicity 1 x = 0 multiplicity 2 x-intercepts: (2, 0), (2, 0) crosses through (0, 0) touches only Example continued as, x y (2, 0) (0, 0) (2, 0) Slide 13 Copyright by Houghton Mifflin Company, Inc. All rights reserved. 13 Example Continued Example continued: Sketch the graph of f (x) = 4x 2 x 4. 3. Since f (x) = 4(x) 2 (x) 4 = 4x 2 x 4 = f (x), the graph is symmetrical about the y-axis. 4. Plot additional points and their reflections in the y-axis: (1.5, 3.9) and (1.5, 3.9 ), ( 0.5, 0.94 ) and (0.5, 0.94) 5. Draw the graph. x y (1.5, 3.9) (1.5, 3.9 ) ( 0.5, 0.94 ) (0.5, 0.94) Slide 14 The Intermediate Value Theorem Let a and b be real numbers such that a < b. If f is a polynomial function such that f(a) f(b) then in the interval [a, b], f takes on every value between f(a) and f(b). Slide 15 There is a zero Since f(1)= -6 f(3) = 4 We know that for 1< x < 3 There is an x such that f(x)=0 Slide 16 Homework 1 - 8, Matching 13-21 odd, 27 - 83 odd Slide 17 1-8 A Matching 1.f(x) = -2x + 3 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5.f(x) = - x 4 + 3x 2 6.f(x) = -1/3 x 3 + x 2 4/3 7.f(x) = x 4 + 2x 3 8.f(x) = 1/5 x 5 -2x 3 + 9/5 x A Slide 18 1-8 B Matching 1.f(x) = -2x + 3 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5.A 6.f(x) = -1/3 x 3 + x 2 4/3 7.f(x) = x 4 + 2x 3 8.f(x) = 1/5 x 5 -2x 3 + 9/5 x B Slide 19 1-8 C Matching 1.f(x) = -2x + 3 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5. A 6.f(x) = -1/3 x 3 + x 2 4/3 7.f(x) = x 4 + 2x 3 8.B C Slide 20 1-8 D Matching 1.C 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5.A 6.f(x) = -1/3 x 3 + x 2 4/3 7.f(x) = x 4 + 2x 3 8.B D Slide 21 1-8 E Matching 1. C 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5.A 6.f(x) = -1/3 x 3 + x 2 4/3 7.D 8.B E Slide 22 1-8 F Matching 1. C 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.f(x) = 2x 3 3x + 1 5.A 6.E 7.D 8.B F Slide 23 1-8 G Matching 1. C 2.f(x) = x 2 4x 3.f(x) = -2x 2 5x 4.F 5.A 6.E 7.D 8.B G Slide 24 1-8 H Matching 1. C 2.G 3.f(x) = -2x 2 5x 4.F 5.A 6.E 7.D 8.B H Slide 25 #37 g(t) = t 5 6t 3 + 9t g(t) = t 5 6t 3 + 9t g(t) = t(t 4 6t 2 + 9) g(t) = t(t 2 3) 2

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