-2y(2y-3)=-20

Solution for -2y(2y-3)=-20 equation:

-2y(2y-3)=-20

We move all terms to the left:

-2y(2y-3)-(-20)=0

We add all the numbers together, and all the variables

-2y(2y-3)+20=0

We multiply parentheses

-4y^2+6y+20=0

a = -4; b = 6; c = +20;
Δ = b2-4ac
Δ = 62-4·(-4)·20
Δ = 356
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:

$\sqrt{\Delta}=\sqrt{356}=\sqrt{4*89}=\sqrt{4}*\sqrt{89}=2\sqrt{89}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-2\sqrt{89}}{2*-4}=\frac{-6-2\sqrt{89}}{-8}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+2\sqrt{89}}{2*-4}=\frac{-6+2\sqrt{89}}{-8}
$