#### Answer

$f(x) = 6|x+2|$

#### Work Step by Step

Write 36 as $6^2$, and then simplify to obtain:
$f(x)=\sqrt{6^2(x+2)^2}
\\f(x)=6\sqrt{(x+2)^2}$
RECALL:
(i) $\sqrt{a^2} = a$ when $a \ge 0$
(ii) $\sqrt{a^2} = |a|$ when $a \lt 0$
$x$ can be any real number. This means that when $x \lt -2$, the value of $x+2$ is negative.
Thus, to simplify $f(x)=6\sqrt{(x+2)^2}$, rule (ii) above must be used.
Therefore,
$f(x) = 6|x+2|$