# How do you solve x^2-1=80?

Jul 25, 2016

$x = \pm 9$

#### Explanation:

${x}^{2} - 1 = 80$

$\Rightarrow {x}^{2} - 81 = 0$

$\Rightarrow \left(x + 9\right) \left(x - 9\right) = 0$

$\Rightarrow x = \pm 9$ is the solution.