Answer
$6|x|$
Work Step by Step
In this exercise, $36$ is a perfect square, and $x^2$ is also a perfect square. Take the square roots of $36$ and $x^2$:
$6x$
According to the $n$th root of $n$th Powers Property, which states that for any number $a$, for the expression $\sqrt[n] {a^n}$, if $n$, which is both the value of the index and of the exponent, is even, then we need to put $a$ inside absolute value sign:
$6|x|$
