# How do you factor the expression 9x² - 1?

Dec 6, 2015

 color(blue)((3x+1)(3x-1)

#### Explanation:

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

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

As per property
color(blue)(a^2-b^2=(a+b)(a-b)

So for the given expression
color(blue)(a=3x
color(blue)(b=1

(3x)^2 - 1^2= color(blue)((3x+1)(3x-1)