(3y+9)*(3y+9)=81

Solution for (3y+9)*(3y+9)=81 equation:

(3y+9)(3y+9)=81

We move all terms to the left:

(3y+9)(3y+9)-(81)=0

We multiply parentheses ..

(+9y^2+27y+27y+81)-81=0

We get rid of parentheses

9y^2+27y+27y+81-81=0

We add all the numbers together, and all the variables

9y^2+54y=0

a = 9; b = 54; c = 0;
Δ = b2-4ac
Δ = 542-4·9·0
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(54)-54}{2*9}=\frac{-108}{18}
=-6
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(54)+54}{2*9}=\frac{0}{18}
=0
$