# How do you factor 49x^2 -81 ?

Mar 22, 2018

$\left(7 x + 9\right) \left(7 x - 9\right)$

#### Explanation:

Given -

$49 {x}^{2} - 81$

It is in the form ${a}^{2} - {b}^{2}$

Factors for the expression ${a}^{2} - {b}^{2}$ is $\left(a + b\right) \left(a - b\right)$

Following this, we can find the factors for the given expression $49 {x}^{2} - 81$

$\left(7 x + 9\right) \left(7 x - 9\right)$