How do you factor completely 4x² - 36?

Aug 28, 2016

$4 {x}^{2} - 36 = 4 \left(x - 3\right) \left(x + 3\right)$

Explanation:

The difference of squares identity can be written:

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

So we find:

$4 {x}^{2} - 36$

$= 4 \left({x}^{2} - 9\right)$

$= 4 \left({x}^{2} - {3}^{2}\right)$

$= 4 \left(x - 3\right) \left(x + 3\right)$