$$Y=3 { x }^{ 2 } +4 { x }^{ 2 }$$
$x=-\frac{\sqrt{7Y}}{7}$
$x=\frac{\sqrt{7Y}}{7}$
$Y=7x^{2}$
$x=\frac{\sqrt{7Y}}{7}$
$x=-\frac{\sqrt{7Y}}{7}\text{, }Y\geq 0$
