Math Help - Calculating limit

1. Calculating limit

Not sure how to do this limit, I was thinking of rationalizing the denominator but that didn't work.

$\lim_{x \to -4} \frac{1}{\sqrt{x^2+16}}$

2. There is no reason to do that.
$\displaystyle \lim _{x \to - 4} \sqrt {x^2 + 16} = 4\sqrt 2$