-4x(2x-3)=-20

Solution for -4x(2x-3)=-20 equation:

-4x(2x-3)=-20

We move all terms to the left:

-4x(2x-3)-(-20)=0

We add all the numbers together, and all the variables

-4x(2x-3)+20=0

We multiply parentheses

-8x^2+12x+20=0

a = -8; b = 12; c = +20;
Δ = b2-4ac
Δ = 122-4·(-8)·20
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-28}{2*-8}=\frac{-40}{-16}
=2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+28}{2*-8}=\frac{16}{-16}
=-1
$