$${ 2 }^{ x-y } = { x }^{ 2 } -9$$
$y=-\log_{2}\left(x^{2}-9\right)-\frac{2\pi n_{1}i}{\ln(2)}+x$
$n_{1}\in \mathrm{Z}$
$x\neq 3\text{ and }x\neq -3$
$y=-\log_{2}\left(x^{2}-9\right)+x$
$|x|>3$
