$$\left. \begin{array} { l } { x ^ { 2 } + 4 x + y ^ { 2 } - 2 y - 4 = 0 \right.$$
$x=\sqrt{-\left(y-4\right)\left(y+2\right)}-2$
$x=-\sqrt{-\left(y-4\right)\left(y+2\right)}-2$
$x=\sqrt{\left(4-y\right)\left(y+2\right)}-2$
$x=-\sqrt{\left(4-y\right)\left(y+2\right)}-2\text{, }y\geq -2\text{ and }y\leq 4$
