-x2+16x+80=0

Solution for -x2+16x+80=0 equation:

-x2+16x+80=0

We add all the numbers together, and all the variables

-1x^2+16x+80=0

a = -1; b = 16; c = +80;
Δ = b2-4ac
Δ = 162-4·(-1)·80
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-24}{2*-1}=\frac{-40}{-2}
=+20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+24}{2*-1}=\frac{8}{-2}
=-4
$