Answer
$36-16\sqrt{5}$.
Work Step by Step
The given expression is
$=(2\sqrt{5}-4)^2$
Use formula $(a-b)^2=a^2-2ab+b^2$.
We have $a=2\sqrt{5}$ and $b=4$.
$=(2\sqrt{5})^2-2(2\sqrt{5})(4)+(4)^2$
Simplify.
$=4\cdot 5-16\sqrt{5}+16$
$=20-16\sqrt{5}+16$
Add like terms.
$=36-16\sqrt{5}$.
