-8x^2+68x+220=0

Solution for -8x^2+68x+220=0 equation:

-8x^2+68x+220=0

a = -8; b = 68; c = +220;
Δ = b2-4ac
Δ = 682-4·(-8)·220
Δ = 11664
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{11664}=108$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(68)-108}{2*-8}=\frac{-176}{-16}
=+11
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(68)+108}{2*-8}=\frac{40}{-16}
=-2+1/2
$