3.5 Higher – Degree Polynomial Functions and Graphs.
Post on 31-Mar-2015
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3.5 Higher Degree Polynomial Functions and Graphs Slide 2 Polynomial Function Definition: A polynomial function of degree n in the variable x is a function defined by Where each a i (0 i n-1) is a real number, a n 0, and n is a whole number. Whats the domain of a polynomial function? P(x) = a n x n + a n-1 x n-1 + + a 1 x + a 0 Slide 3 Get to know a polynomial function P(x) = a n x n + a n-1 x n-1 + + a 1 x + a 0 a n : Leading coefficient a n x n : Dominating term a 0 : Constant term Slide 4 Cubic Functions P(x) = ax 3 + bx 2 + cx + d (b)(a) (d)(c) Slide 5 Quartic Functions P(x) = ax 4 + bx 3 + cx 2 + dx + e (b)(a) (d)(c) Slide 6 Extrema Turning points: points where the function changes from increasing to decreasing or vice versa. Local maximum point: the highest point at a peak. The corresponding function values are called local maxima. Local minimum point: the lowest point at a valley. The corresponding function values are called local minima. Extrema: either local maxima or local minima. Slide 7 Absolute and Local Extrema Let c be in the domain of P. Then (a) P(c) is an absolute maximum if P(c) P(x) for all x in the domain of P. (b) P(c) is an absolute minimum if P(c) P(x) for all x in the domain of P. (c) P(c) is an local maximum if P(c) P(x) when x is near c. (d) P(c) is an local minimum if P(c) P(x) when x is near c. Slide 8 Example Local minimum point Local minimum point Local minimum & Absolute minimum point Local minimum point Local minimum point A function can only have one and only one absolute minimum of maximum Slide 9 Hidden behavior Hidden behavior of a polynomial function is the function behaviors which are not apparent in a particular window of the calculator. Slide 10 Number of Turning Points The number of turning points of the graph of a polynomial function of degree n 1 is at most n 1. Example: f(x) = x f(x) = x 2 f(x) = x 3 Slide 11 End Behavior Definition: The end behavior of a polynomial function is the increasing of decreasing property of the function when its independent variable reaches to or - The end behavior of the graph of a polynomial function is determined by the sign of the leading coefficient and the parity of the degree. Slide 12 End Behavior Odd degree a > 0 a < 0 Even degree a > 0 a < 0 Slide 13 example Determining end behavior Given the Polynomial f(x) = x 4 x 2 +5x -4 Slide 14 X Intercepts (Real Zeros) Theorem: The graph of a polynomial function of degree n will have at most n x-intercepts (real zeros). Example: P(x) = x 3 + 5x 2 +5x -2 Slide 15 Comprehensive Graphs A comprehensive graph of a polynomial function will exhibit the following features: 1. all x-intercept (if any) 2. the y-intercept 3. all extreme points(if any) 4. enough of the graph to reveal the correct end behavior Slide 16 example 1. f(x) = 2x 3 x 2 -2 2. f(x) = -2x 3 - 14x 2 + 2x + 84 a) what is the degree? b) Describe the end behavior of the graph. c) What is the y-intercept? d) Find any local/absolute maximum value(s).... local/absolute maximum points. [repeat for minimums] e) Approximate any values of x for which f(x) = 0 Slide 17 Homework PG. 210: 10-50(M5), 60, 63 KEY: 25, 60 Reading: 3.6 Polynomial Fncs (I)