2x^2+56x-640=0

Solution for 2x^2+56x-640=0 equation:

2x^2+56x-640=0

a = 2; b = 56; c = -640;
Δ = b2-4ac
Δ = 562-4·2·(-640)
Δ = 8256
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:

$\sqrt{\Delta}=\sqrt{8256}=\sqrt{64*129}=\sqrt{64}*\sqrt{129}=8\sqrt{129}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(56)-8\sqrt{129}}{2*2}=\frac{-56-8\sqrt{129}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(56)+8\sqrt{129}}{2*2}=\frac{-56+8\sqrt{129}}{4}
$