#### Answer

$x_{1}=2$ and $x_{2}=-2$

#### Work Step by Step

Given $9y^2=36 , $ dividing by 9 both sides of the equation, we have:
$9y^2=36 \longrightarrow y^2=4 \longrightarrow y^2-4=0$
Where $a=1,\ b=0,\ c=-4$
Using the quadratic formula: $\dfrac{-b\pm \sqrt{b^2-4ac}}{2a} , $ we have:
$\dfrac{-0\pm \sqrt{0^2-4\times 1\times (-4)}}{2\times 1} = \dfrac{\pm \sqrt{16}}{2} = \pm \dfrac{ 4}{2} = \pm2$
Therefore the solutions are: $x_{1}=2$ and $x_{2}=-2$