Factor 9-y^2

$9 - y^{2}$

Step 1

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

$3^{2} - y^{2}$

Step 2

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

$(3 + y) (3 - y)$