# How do you simplify 4 / sqrt 5?

$\frac{4}{\sqrt{5}} = \frac{4}{5} \sqrt{5}$
$\textcolor{w h i t e}{\text{XXXXXXXX}}$ which some would consider a "simplification".
$\frac{4}{\sqrt{5}} = \frac{4}{\sqrt{5}} \cdot \frac{\sqrt{5}}{\sqrt{5}} = \frac{4 \sqrt{5}}{\sqrt{5} \cdot \sqrt{5}} = \frac{4 \sqrt{5}}{5}$