-2x^2+80x-11=0

Solution for -2x^2+80x-11=0 equation:

-2x^2+80x-11=0

a = -2; b = 80; c = -11;
Δ = b2-4ac
Δ = 802-4·(-2)·(-11)
Δ = 6312
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:

$\sqrt{\Delta}=\sqrt{6312}=\sqrt{4*1578}=\sqrt{4}*\sqrt{1578}=2\sqrt{1578}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(80)-2\sqrt{1578}}{2*-2}=\frac{-80-2\sqrt{1578}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(80)+2\sqrt{1578}}{2*-2}=\frac{-80+2\sqrt{1578}}{-4}
$