We shouls find the zeros of the following polynomial function:
f(x)=x^3-x^2-20x
We can rewrite it in order to obtain function easier to solve:
f(x)=x(x^2-x-20)
x^2-x-20=(x-4)(x+5)
f(x)=x(x-4)(x+5)
So the zeros of the polynomial function f(x)=x^3-x^2-20x are -5,0,4.