How do you simplify 2/sqrt5?

Multiply the numerator and denominator times $\sqrt{5}$.
$\frac{2}{\sqrt{5}} \cdot \frac{\sqrt{5}}{\sqrt{5}} = \frac{2 \sqrt{5}}{5}$
Try rationalizing by multiplying and dividing by $\sqrt{5}$., i.e.:
$\frac{2}{\sqrt{5}} \cdot \frac{\sqrt{5}}{\sqrt{5}} =$ and see what happens!