Factor r^2-9

$r^{2} - 9$

Step 1

Rewrite $9$ as $3^{2}$ .

$r^{2} - 3^{2}$

Step 2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = r$ and $b = 3$ .

$(r + 3) (r - 3)$