-40x^2+320x=0

Solution for -40x^2+320x=0 equation:

-40x^2+320x=0

a = -40; b = 320; c = 0;
Δ = b2-4ac
Δ = 3202-4·(-40)·0
Δ = 102400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{102400}=320$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(320)-320}{2*-40}=\frac{-640}{-80}
=+8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(320)+320}{2*-40}=\frac{0}{-80}
=0
$