# How do you solve x^2-9=0?

Apr 28, 2016

$x = - 3$ or $x = 3$

#### Explanation:

In ${x}^{2} - 9 = 0$, add and subtract $3 x$, this leads to

${x}^{2} + 3 x - 3 x - 9 = 0$

or $x \left(x + 3\right) - 3 \left(x + 3\right) = 0$

or $\left(x - 3\right) \left(x + 3\right) = 0$

As product of $x + 3$ and $x - 3$ is zero,

either $x + 3 = 0$ or $x - 3 = 0$

i.e. $x = - 3$ or $x = 3$