-4x^2+120x=0

Solution for -4x^2+120x=0 equation:

-4x^2+120x=0

a = -4; b = 120; c = 0;
Δ = b2-4ac
Δ = 1202-4·(-4)·0
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-120}{2*-4}=\frac{-240}{-8}
=+30
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+120}{2*-4}=\frac{0}{-8}
=0
$