# What are the zeros of x^2-9 ?

Apr 16, 2017

$x = 3$ and $x = - 3$

#### Explanation:

The difference of squares identity can be written:

${a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$

Note that both ${x}^{2}$ and $9 = {3}^{2}$ are perfect squares, so we find:

${x}^{2} - 9 = {x}^{2} - {3}^{2} = \left(x - 3\right) \left(x + 3\right)$

So the zeros are $3$ and $- 3$