Polynomial Functions and Graphs

AAT-A IB - HR Date: 2/25/2014 ID Check Objective: SWBAT evaluate polynomial functions. Bell Ringer: Check Homework HW Requests: Pg 350 #16-36 evens In class: pg 350 #17-3 by 4’s 40, 42, 44, HW: pg 350 #37-52 Read Section 7.2 Announcements: Quiz this week “ There is something in every one of you that waits and listens for the sound of the genuine in yourself. It is the only true guide you will ever have. And if you cannot hear it, you will all of your life spend your days on the ends of strings that somebody else pulls.” ― Howard ThurmanHoward Thurman Maximize Academic Potential Turn UP! MAP

Higher Degree Polynomial Functions and Graphs  a n is called the leading coefficient  n is the degree of the polynomial  a 0 is called the constant term Polynomial Function A polynomial function of degree n in the variable x is a function defined by where each a i is real, a n  0, and n is a whole number.

x-Intercepts (Real Zeros) Number Of x-Intercepts of a Polynomial Function A polynomial function of degree n will have a maximum of n x- intercepts (real zeros). Find all zeros of f (x) = -x 4 + 4x 3 - 4x 2.  x 4  4x 3  4x 2  We now have a polynomial equation. x 4  4x 3  4x 2  0 Multiply both sides by  1. (optional step) x 2 (x 2  4x  4)  0 Factor out x 2. x 2 (x  2) 2  0 Factor completely. x 2  or (x  2) 2  0 Set each factor equal to zero. x  0 x  2 Solve for x. (0,0) (2,0)

Polynomial Functions The largest exponent within the polynomial determines the degree of the polynomial. Polynomial Function in General Form Degree Name of Function 1Linear 2Quadratic 3Cubic 4Quartic

Polynomial Functions f(x) = 3 ConstantFunction Degree = 0 Maximum Number of Zeros: 0

f(x) = x + 2 LinearFunction Degree = 1 Maximum Number of Zeros: 1 Polynomial Functions

f(x) = x 2 + 3x + 2 QuadraticFunction Degree = 2 Maximum Number of Zeros: 2 Polynomial Functions

f(x) = x 3 + 4x Cubic Function Degree = 3 Maximum Number of Zeros: 3 Polynomial Functions

Quartic Function Degree = 4 Maximum Number of Zeros: 4 Polynomial Functions

Leading Coefficient The leading coefficient is the coefficient of the first term in a polynomial when the terms are written in descending order by degrees. For example, the quartic function f(x) = -2x 4 + x 3 – 5x 2 – 10 has a leading coefficient of -2.

Slide Leading Coefficient Test for Polynomial End Behavior Leading Coefficient Test leading coefficient degree of polynomial LeftRight +even ↑ +↑ + ↑ + +odd ↓ - ↑+↑+ -even ↓-↓- ↓ - -odd ↑ + ↓-↓-

Example Use the Leading Coefficient Test to determine the end behavior of the graph of f (x)  x 3  3x 2  x  3. Falls left y Rises right x

Determining End Behavior Match each function with its graph. A. B. C. D.

Quartic Polynomials Look at the two graphs and discuss the questions given below. 1. How can you check to see if both graphs are functions? 3. What is the end behavior for each graph? 4. Which graph do you think has a positive leading coeffient? Why? 5. Which graph do you think has a negative leading coefficient? Why? 2. How many x-intercepts do graphs A & B have? Graph B Graph A

Extrema  Turning points – where the graph of a function changes from increasing to decreasing or vice versa. The number of turning points of the graph of a polynomial function of degree n  1 is at most n – 1.  Local maximum point – highest point or “peak” in an interval function values at these points are called local maxima  Local minimum point – lowest point or “valley” in an interval function values at these points are called local minima  Extrema – plural of extremum, includes all local maxima and local minima

Extrema

Number of Local Extrema  A linear function has degree 1 and no local extrema.  A quadratic function has degree 2 with one extreme point.  A cubic function has degree 3 with at most two local extrema.  A quartic function has degree 4 with at most three local extrema.  How does this relate to the number of turning points?

The Leading Coefficient Test As x increases or decreases without bound, the graph of the polynomial function f (x)  a n x n  a n-1 x n-1  a n-2 x n-2  …  a 1 x  a 0 (a n  0) eventually rises or falls. In particular, For n odd:a n  0 a n  0 As x increases or decreases without bound, the graph of the polynomial function f (x)  a n x n  a n-1 x n-1  a n-2 x n-2  …  a 1 x  a 0 (a n  0) eventually rises or falls. In particular, For n odd:a n  0 a n  0 If the leading coefficient is positive, the graph falls to the left and rises to the right. If the leading coefficient is negative, the graph rises to the left and falls to the right. Rises right Falls left Falls right Rises left

As x increases or decreases without bound, the graph of the polynomial function f (x)  a n x n  a n-1 x n-1  a n-2 x n-2  …  a 1 x  a 0 (a n  0) eventually rises or falls. In particular, For n even: a n  0 a n  0 As x increases or decreases without bound, the graph of the polynomial function f (x)  a n x n  a n-1 x n-1  a n-2 x n-2  …  a 1 x  a 0 (a n  0) eventually rises or falls. In particular, For n even: a n  0 a n  0 If the leading coefficient is positive, the graph rises to the left and to the right. If the leading coefficient is negative, the graph falls to the left and to the right. Rises right Rises left Falls left Falls right The Leading Coefficient Test

Comprehensive Graphs  The most important features of the graph of a polynomial function are: 1. intercepts, 2. extrema, 3. end behavior.  A comprehensive graph of a polynomial function will exhibit the following features: 1. all x-intercepts (if any), 2. the y-intercept, 3. all extreme points (if any), 4. enough of the graph to exhibit end behavior.

Multiplicity and x-Intercepts If r is a zero of even multiplicity, then the graph touches the x-axis and turns around at r. If r is a zero of odd multiplicity, then the graph crosses the x-axis at r. Regardless of whether a zero is even or odd, graphs tend to flatten out at zeros with multiplicity greater than one.

Example  Find the x-intercepts and multiplicity of f(x) =2(x+2) 2 (x-3 )  Zeros are at (-2,0) (3,0)