-2y(y-5)=8

Solution for -2y(y-5)=8 equation:

-2y(y-5)=8

We move all terms to the left:

-2y(y-5)-(8)=0

We multiply parentheses

-2y^2+10y-8=0

a = -2; b = 10; c = -8;
Δ = b2-4ac
Δ = 102-4·(-2)·(-8)
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-6}{2*-2}=\frac{-16}{-4}
=+4
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+6}{2*-2}=\frac{-4}{-4}
=1
$