# Question #3c24d

Apr 12, 2017

$\left(5 - h\right) \left(5 + h\right)$

#### Explanation:

First, note that 25 is a square number, namely $25 = {5}^{2}$

Second, be aware of this expansion, ${a}^{2} - {b}^{2} = \left(a + b\right) \left(a - b\right)$, and this expansion is known as the "difference of two squares", because you are subtracting one square number from another.

Applying this, we see that:
$25 - {h}^{2} = {5}^{2} - {h}^{2}$
$= \left(5 - h\right) \left(5 + h\right)$