-(X^2)+4x+80=0

Solution for -(X^2)+4x+80=0 equation:

-(X^2)+4X+80=0

We add all the numbers together, and all the variables

-1X^2+4X+80=0

a = -1; b = 4; c = +80;
Δ = b2-4ac
Δ = 42-4·(-1)·80
Δ = 336
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:

$\sqrt{\Delta}=\sqrt{336}=\sqrt{16*21}=\sqrt{16}*\sqrt{21}=4\sqrt{21}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-4\sqrt{21}}{2*-1}=\frac{-4-4\sqrt{21}}{-2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+4\sqrt{21}}{2*-1}=\frac{-4+4\sqrt{21}}{-2}
$