#### Answer

$-|x|$

#### Work Step by Step

As shown on page 437, $\sqrt[n] a^{n}=|a|$ when $n$ is an even positive integer.
In this case, we know that $\sqrt (x^{2})$ is equivalent to $\sqrt[2] (x^{2})$, since we are taking the square root.
Therefore, we know that $\sqrt (x^{2})=\sqrt[2] (x^{2})=|x|$.
As a result, $-\sqrt (x^{2})=-|x|$.