# How do you factor 36x^3-9x?

May 20, 2016

$9 x \left(2 x - 1\right) \left(2 x + 1\right)$

#### Explanation:

Note that $4 \times 9 = 36$

$\implies 9 x \left(4 {x}^{2} - 1\right)$

Consider the standard form of $\text{ } {a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$

Note that $4 {x}^{2} \to {\left(2 x\right)}^{2} \text{ and } 1 = {1}^{2}$

$9 x \left[{\left(2 x\right)}^{2} - {1}^{2}\right]$

$9 x \left(2 x - 1\right) \left(2 x + 1\right)$