Answer
$2\sqrt{5}$.
Work Step by Step
The given expression is
$=\sqrt{20}$
Factor as square terms.
$=\sqrt{4\cdot 5}$
Use product property of square roots.
$=\sqrt{4}\cdot \sqrt{5}$
Use $4=2^2$.
$=\sqrt{2^2}\cdot \sqrt{5}$
Simplify.
$=2\sqrt{5}$.
