-2x^2+640x-30000=0

Solution for -2x^2+640x-30000=0 equation:

-2x^2+640x-30000=0

a = -2; b = 640; c = -30000;
Δ = b2-4ac
Δ = 6402-4·(-2)·(-30000)
Δ = 169600
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:

$\sqrt{\Delta}=\sqrt{169600}=\sqrt{1600*106}=\sqrt{1600}*\sqrt{106}=40\sqrt{106}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(640)-40\sqrt{106}}{2*-2}=\frac{-640-40\sqrt{106}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(640)+40\sqrt{106}}{2*-2}=\frac{-640+40\sqrt{106}}{-4}
$