Factor 4-y^2

$4 - y^{2}$

Step 1

Rewrite $4$ as $2^{2}$ .

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

Step 2

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

$(2 + y) (2 - y)$