We want to find the zeros and sketch the graph of the given polynomial function.
p(x)=x^3-5x^2-4x+20
Let's do these things one at a time.
Zeros of the Function
To find the zeros, we need to find the values of x for which p(x)=0.
p(x)=0 ⇔ x^3-5x^2-4x+20=0Since the function is not written in factored form, we will begin by factoring the equation.
We found that the zeros of the function are x=-2, x=2, and x=5.
Graph
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^3-5x^2-4x+20
p(x)=x^3-5x^2-4x+20
- 3
( - 3)^3-5( - 3)^2-4( - 3)+20
-40
0
0^3-5( 0)^2-4( 0)+20
20
4
4^3-5( 4)^2-4( 4)+20
-12
6
6^3-5( 6)^2-4( 6)+20
32
The points ( - 3, -40), ( 0, 20), ( 4, -12), and ( 6, 32) are on the graph of the function. Now, we will determine the leading coefficient and degree of the polynomial function.
p(x)=x^3-5x^2-4x+20
⇕
p(x)=1x^()magenta3-5x^2-4x+20
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. With this in mind, let's plot the zeros and the obtained points, and graph the function.
