9y2-9=18

Solution for 9y2-9=18 equation:

9y^2-9=18

We move all terms to the left:

9y^2-9-(18)=0

We add all the numbers together, and all the variables

9y^2-27=0

a = 9; b = 0; c = -27;
Δ = b2-4ac
Δ = 02-4·9·(-27)
Δ = 972
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{972}=\sqrt{324*3}=\sqrt{324}*\sqrt{3}=18\sqrt{3}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-18\sqrt{3}}{2*9}=\frac{0-18\sqrt{3}}{18}
=-\frac{18\sqrt{3}}{18}
=-\sqrt{3}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+18\sqrt{3}}{2*9}=\frac{0+18\sqrt{3}}{18}
=\frac{18\sqrt{3}}{18}
=\sqrt{3}
$