-2x^2-28x+80=0

Solution for -2x^2-28x+80=0 equation:

-2x^2-28x+80=0

a = -2; b = -28; c = +80;
Δ = b2-4ac
Δ = -282-4·(-2)·80
Δ = 1424
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:

$\sqrt{\Delta}=\sqrt{1424}=\sqrt{16*89}=\sqrt{16}*\sqrt{89}=4\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-4\sqrt{89}}{2*-2}=\frac{28-4\sqrt{89}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+4\sqrt{89}}{2*-2}=\frac{28+4\sqrt{89}}{-4}
$