Answer
$x=\pm\frac{\sqrt y}{3}$
When output $y=2$, input $x=\pm\frac{\sqrt 2}{3}$
Work Step by Step
$y=9x^{2}$
Divide both sides of the equation by $9$ to get
$\frac{y}{9}=x^{2}$
Taking square root on both sides, we have
$\pm\frac{\sqrt y}{3}=x$
That is, $x=\pm\frac{\sqrt y}{3}$
When output $y=2$,
Input $x=\pm\frac{\sqrt 2}{3}$
