20b^2-8b-64=0

Solution for 20b^2-8b-64=0 equation:

20b^2-8b-64=0

a = 20; b = -8; c = -64;
Δ = b2-4ac
Δ = -82-4·20·(-64)
Δ = 5184
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5184}=72$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-72}{2*20}=\frac{-64}{40}
=-1+3/5
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+72}{2*20}=\frac{80}{40}
=2
$