-16x^2+14x+640=0

Solution for -16x^2+14x+640=0 equation:

-16x^2+14x+640=0

a = -16; b = 14; c = +640;
Δ = b2-4ac
Δ = 142-4·(-16)·640
Δ = 41156
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:

$\sqrt{\Delta}=\sqrt{41156}=\sqrt{4*10289}=\sqrt{4}*\sqrt{10289}=2\sqrt{10289}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-2\sqrt{10289}}{2*-16}=\frac{-14-2\sqrt{10289}}{-32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+2\sqrt{10289}}{2*-16}=\frac{-14+2\sqrt{10289}}{-32}
$