# How do you factor the expression 9x^2-1?

Jan 13, 2016

 color(blue)((3x+1)(3x-1) is the factorised form of the expression

#### Explanation:

$9 {x}^{2} - 1$

The expression can be written as :
${\left(3 x\right)}^{2} - {1}^{2}$

This is of the form
color(blue)(a^2-b^2 = (a+b)(a-b)

Applying the same:
(3x)^2 -1^2 = color(blue)((3x+1)(3x-1)