$$y=-(x+1)^{2}-3$$
$y=-\left(\left(x+1\right)^{2}+3\right)$
$x=-i\sqrt{y+3}-1$
$x=i\sqrt{y+3}-1$
$x=-\left(\sqrt{-y-3}+1\right)$
$x=\sqrt{-y-3}-1\text{, }y\leq -3$
