Answer:
B: x=-5 and x=4
Step-by-step explanation:
f(x)= x^2 + x -20
To find the zeros we replace f(x) with 0
[tex]0= x^2 + x -20[/tex]
now we solve for x
LEts factor x^2 + x -20
sum is +1 and product is -20
5 * (-4)= -20
5 + (-4) = +1
x^2 + 5x - 4x - 20 = 0
(x^2 + 5x)+(- 4x - 20) = 0
x(x+5) -4 (x+5) = 0
(x-4)(x+5)=0
Set each factor =0 and solve for x
x- 4 =0 so x=4
x+5 =0 so x=-5
x=-5 and x=4
