-4x(x-6)=20

Solution for -4x(x-6)=20 equation:

-4x(x-6)=20

We move all terms to the left:

-4x(x-6)-(20)=0

We multiply parentheses

-4x^2+24x-20=0

a = -4; b = 24; c = -20;
Δ = b2-4ac
Δ = 242-4·(-4)·(-20)
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(24)-16}{2*-4}=\frac{-40}{-8}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(24)+16}{2*-4}=\frac{-8}{-8}
=1
$