(9+y)*y=1620

Solution for (9+y)*y=1620 equation:

(9+y)*y=1620

We move all terms to the left:

(9+y)*y-(1620)=0

We add all the numbers together, and all the variables

(y+9)*y-1620=0

We multiply parentheses

y^2+9y-1620=0

a = 1; b = 9; c = -1620;
Δ = b2-4ac
Δ = 92-4·1·(-1620)
Δ = 6561
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6561}=81$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-81}{2*1}=\frac{-90}{2}
=-45
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+81}{2*1}=\frac{72}{2}
=36
$