# How do you find the domain of f(x) = 2 / (1 - x^2)?

In this function you want to avoid values of $x$ of the domain that makes the denominator equal to zero. So you need:
$1 - {x}^{2} \ne 0$
$x \ne \pm 1$
So your domain will be all the real $x$ except $+ 1$ and $- 1$.