## Algebra: A Combined Approach (4th Edition)

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