5b^2-8b-315=0

Solution for 5b^2-8b-315=0 equation:

5b^2-8b-315=0

a = 5; b = -8; c = -315;
Δ = b2-4ac
Δ = -82-4·5·(-315)
Δ = 6364
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{6364}=\sqrt{4*1591}=\sqrt{4}*\sqrt{1591}=2\sqrt{1591}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-2\sqrt{1591}}{2*5}=\frac{8-2\sqrt{1591}}{10}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+2\sqrt{1591}}{2*5}=\frac{8+2\sqrt{1591}}{10}
$