Nov 5, 2015

Try and get some squares out of under the radical.

#### Explanation:

$\sqrt{32} = \sqrt{16 \cdot 2} = \sqrt{16} \cdot \sqrt{2} = 4 \sqrt{2}$
$\sqrt{8} = \sqrt{4 \cdot 2} = \sqrt{4} \cdot \sqrt{2} = 2 \sqrt{2}$

Since the numbers under the radicals are the same you may now safely subtract:

$4 \sqrt{2} - 2 \sqrt{2} = \left(4 - 2\right) \cdot \sqrt{2} = 2 \sqrt{2}$