-8x^2-12x+56=0

Solution for -8x^2-12x+56=0 equation:

-8x^2-12x+56=0

a = -8; b = -12; c = +56;
Δ = b2-4ac
Δ = -122-4·(-8)·56
Δ = 1936
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1936}=44$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-44}{2*-8}=\frac{-32}{-16}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+44}{2*-8}=\frac{56}{-16}
=-3+1/2
$