8y(-5y-15)=36

Solution for 8y(-5y-15)=36 equation:

8y(-5y-15)=36

We move all terms to the left:

8y(-5y-15)-(36)=0

We multiply parentheses

-40y^2-120y-36=0

a = -40; b = -120; c = -36;
Δ = b2-4ac
Δ = -1202-4·(-40)·(-36)
Δ = 8640
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:

$\sqrt{\Delta}=\sqrt{8640}=\sqrt{576*15}=\sqrt{576}*\sqrt{15}=24\sqrt{15}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-120)-24\sqrt{15}}{2*-40}=\frac{120-24\sqrt{15}}{-80}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-120)+24\sqrt{15}}{2*-40}=\frac{120+24\sqrt{15}}{-80}
$