-8u^2-18u-7=0

Solution for -8u^2-18u-7=0 equation:

-8u^2-18u-7=0

a = -8; b = -18; c = -7;
Δ = b2-4ac
Δ = -182-4·(-8)·(-7)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-10}{2*-8}=\frac{8}{-16}
=-1/2
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+10}{2*-8}=\frac{28}{-16}
=-1+3/4
$