$x=-\sqrt{y^{2}-189}$
$x=\sqrt{y^{2}-189}$

$x=\sqrt{y^{2}-189}$
$x=-\sqrt{y^{2}-189}\text{, }|y|\geq 3\sqrt{21}$

$y=\sqrt{x^{2}+189}$
$y=-\sqrt{x^{2}+189}$