Answer
The domain is {$x \in \mathbb{R}|x\ne\pm4$}.
Work Step by Step
For a fraction to be defined the denominator can not equal to $0$.
The domain can be determined by tfirst looking at the values of $x$ for which the function is not defined:
$x^2-16\ne0$
$x^2\ne16$
$x\ne\pm4$
This requirement can be applied to define the domain:
Therefore the domain is {$x\in\mathbb{R}|x\ne\pm4$}.