-8y(y-9)=-40

Solution for -8y(y-9)=-40 equation:

-8y(y-9)=-40

We move all terms to the left:

-8y(y-9)-(-40)=0

We add all the numbers together, and all the variables

-8y(y-9)+40=0

We multiply parentheses

-8y^2+72y+40=0

a = -8; b = 72; c = +40;
Δ = b2-4ac
Δ = 722-4·(-8)·40
Δ = 6464
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:

$\sqrt{\Delta}=\sqrt{6464}=\sqrt{64*101}=\sqrt{64}*\sqrt{101}=8\sqrt{101}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-8\sqrt{101}}{2*-8}=\frac{-72-8\sqrt{101}}{-16}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+8\sqrt{101}}{2*-8}=\frac{-72+8\sqrt{101}}{-16}
$