Question

Find the zeros of the polynomial function. f(x) = x3 5x2 - 4x - 20

Answer 1

You can factor this by grouping.
(x³ + 5x²) -(4x +20) = x²(x+5) -4(x+5)
= (x² -4)(x +5)
Using the factored form of the difference of squares, this is
= (x -2)(x +2)(x +5)

Zeros are the values of x that make these factors be zero.
x ∈ {-5, -2, 2}