-4y*5y=+8y

Solution for -4y*5y=+8y equation:

-4y*5y=+8y

We move all terms to the left:

-4y*5y-(+8y)=0

Wy multiply elements

-20y^2-(+8y)=0

We get rid of parentheses

-20y^2-8y=0

a = -20; b = -8; c = 0;
Δ = b2-4ac
Δ = -82-4·(-20)·0
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-8}{2*-20}=\frac{0}{-40}
=0
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+8}{2*-20}=\frac{16}{-40}
=-2/5
$