-640x^2-8640x+129600=0

Solution for -640x^2-8640x+129600=0 equation:

-640x^2-8640x+129600=0

a = -640; b = -8640; c = +129600;
Δ = b2-4ac
Δ = -86402-4·(-640)·129600
Δ = 406425600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{406425600}=20160$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8640)-20160}{2*-640}=\frac{-11520}{-1280}
=+9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8640)+20160}{2*-640}=\frac{28800}{-1280}
=-22+1/2
$