y^2+6y-18=18

Solution for y^2+6y-18=18 equation:

y^2+6y-18=18

We move all terms to the left:

y^2+6y-18-(18)=0

We add all the numbers together, and all the variables

y^2+6y-36=0

a = 1; b = 6; c = -36;
Δ = b2-4ac
Δ = 62-4·1·(-36)
Δ = 180
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:

$\sqrt{\Delta}=\sqrt{180}=\sqrt{36*5}=\sqrt{36}*\sqrt{5}=6\sqrt{5}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-6\sqrt{5}}{2*1}=\frac{-6-6\sqrt{5}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+6\sqrt{5}}{2*1}=\frac{-6+6\sqrt{5}}{2}
$