8b^2-11b-15=-8

Solution for 8b^2-11b-15=-8 equation:

8b^2-11b-15=-8

We move all terms to the left:

8b^2-11b-15-(-8)=0

We add all the numbers together, and all the variables

8b^2-11b-7=0

a = 8; b = -11; c = -7;
Δ = b2-4ac
Δ = -112-4·8·(-7)
Δ = 345
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-\sqrt{345}}{2*8}=\frac{11-\sqrt{345}}{16}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+\sqrt{345}}{2*8}=\frac{11+\sqrt{345}}{16}
$