# How do you factor 3x^3 - 3x^2 - 60x?

May 16, 2016

3x(x + 4)(x - 5)

#### Explanation:

$f \left(x\right) = 3 x y = 3 x \left({x}^{2} - x - 20\right)$
factor y, the trinomial in parentheses.
$y = {x}^{2} - x - 20.$
Find 2 numbers knowing sum (b = -1) and product (c = -20). It is the sum (4, -5).
y = (x + 4)(x - 5)
Therefor,
f(x) = 3x(x + 4)(x - 5)