Question

Factor completely:

x³ - 9x

Answer 1

x(x+3)(x-3)

Explanation:

Factor out common term x

=x(x^2-9)

Factor x^2-9;

(x+3)(x-3)

=x(x+3)(x-3)

Answer 2

x(x + 3)(x - 3)

Explanation:

What we're given is a difference of squares multiplied by x. If we start by factoring x out, we can simply expand the binomial:

x³ - 9x

= x(x² - 9)

= x(x + 3)(x - 3)

Any time you see an expression in the format a² - b², that is called a difference of squares, and can always be expanded out to (a + b)(a - b). In this case, a is x, and b is 3.