-20x^2+120x-120=0

Solution for -20x^2+120x-120=0 equation:

-20x^2+120x-120=0

a = -20; b = 120; c = -120;
Δ = b2-4ac
Δ = 1202-4·(-20)·(-120)
Δ = 4800
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4800}=\sqrt{1600*3}=\sqrt{1600}*\sqrt{3}=40\sqrt{3}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-40\sqrt{3}}{2*-20}=\frac{-120-40\sqrt{3}}{-40}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+40\sqrt{3}}{2*-20}=\frac{-120+40\sqrt{3}}{-40}
$