Answer
$|x+2|$
Work Step by Step
We are told that $\sqrt[n] a^{n}=|a|$ when n is an even positive integer.
In this case, we must factor in order to find $a$.
$x^{2}+4x+4=(x+2)(x+2)=(x+2)^{2}$
Therefore, $a=(x+2)$.
$\sqrt (x+2)^{2}=|x+2|$