## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

The domain is {$x\in \mathbb{R}|x\ne\pm2$}.
The domain determined by first looking for the values of $x$ for which the function is not defined. For a fraction to be defined the denominator can not equal to $0$: $x^2-4\ne0$ $x^2\ne4$ $x=\pm\sqrt4$ $x\ne\pm2$ This requirement can be applied to define the domain: Therefore the domain is {$x\in \mathbb{R}|x\ne\pm2$}.