$$f ( x ) = \frac { \sqrt { x + 2 } } { 3 - 3 x ^ { 2 } } , x$$
$f=\frac{\sqrt{x+2}}{3\left(x-x^{3}\right)}$
$x\neq 1\text{ and }x\neq -1\text{ and }x\neq 0$
$f=\frac{\sqrt{x+2}}{3\left(x-x^{3}\right)}$
$x\neq 0\text{ and }x\geq -2\text{ and }|x|\neq 1$