# How do you factor 28u ^ { 4} - 63u ^ { 2}?

Sep 2, 2017

$7 {u}^{2} \left(2 u - 3\right) \left(2 u + 3\right)$

#### Explanation:

First we look for common factors between the terms. You should notice the coefficients both divide by 7.

$7 \left(4 {u}^{4} - 9 {u}^{2}\right)$

Both terms also have ${u}^{2}$ in common, so we can pull that out front as well.

$7 {u}^{2} \left(4 {u}^{2} - 9\right)$

$4 {u}^{2} - 9$ is a difference of squares, so we can factor it too.

$7 {u}^{2} \left(2 u - 3\right) \left(2 u + 3\right)$