Big Ideas Math Algebra 2, 2014
BI
Big Ideas Math Algebra 2, 2014 View details
8. Analyzing Graphs of Polynomial Functions
Continue to next subchapter

Exercise 3 Page 216

A

Practice makes perfect
We want to find the zeros of the given polynomial function. f(x)=(x-1)(x-2)(x+2)

Zeros of the Function

To do so, we need to find the values of x for which f(x)=0. f(x)=0 ⇔ (x-1)(x-2)(x+2)=0 Since the function is already written in factored form, we will use the Zero Product Property.
(x-1)(x-2)(x+2)=0
lcx-1=0 & (I) x-2=0 & (II) x+2=0 & (III)
lx=1 x-2=0 x+2=0
lx=1 x=2 x+2=0
lx=1 x=2 x=- 2
We found that the zeros of the function are 1, 2, and - 2. We can stop here and recognize that the only graph with those zeros is graph A.

Extra

Graphing the function using a table of values

To draw the graph of the function, we will find some additional points and consider the end behavior. Let's use a table to find additional points.

x (x-1)(x-2)(x+2) f(x)=(x-1)(x-2)(x+2)
- 2 ( - 2-1)( - 2-2)( - 2+2) 0
- 1 ( - 1-1)( - 1-2)( - 1+2) 6
0 ( 0-1)( 0-2)( 0+2) 4
1 ( 1-1)( 1-2)( 1+2) 0
The points ( - 2, 0), ( - 1, 6), ( 0, - 4), and ( 1, 0) are on the graph of the function. Finally, let's apply the Distributive Property. This will simplify the equation and determine the leading coefficient and degree of the polynomial function.
y=(x-1)(x-2)(x+2)
â–Ľ
Multiply
y=(x-1)(x(x+2)-2(x+2))
y=(x-1)(x^2+2x-2(x+2))
y=(x-1)(x^2+2x-2x-4)
y=(x-1)(x^2-4)
y=x^2(x-1)-4(x-1)
y=x^3-x^2-4(x-1)
y=x^3-x^2-4x+4
We can see now that the leading coefficient is 1, which is a positive number. Also, the degree is 3, which is an odd number. Therefore, the end behavior is down and up. Now, let's draw the graph!