-8x^2-11x+56=0

Solution for -8x^2-11x+56=0 equation:

-8x^2-11x+56=0

a = -8; b = -11; c = +56;
Δ = b2-4ac
Δ = -112-4·(-8)·56
Δ = 1913
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-\sqrt{1913}}{2*-8}=\frac{11-\sqrt{1913}}{-16}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+\sqrt{1913}}{2*-8}=\frac{11+\sqrt{1913}}{-16}
$