-5b^2-4b+1=0

Solution for -5b^2-4b+1=0 equation:

-5b^2-4b+1=0

a = -5; b = -4; c = +1;
Δ = b2-4ac
Δ = -42-4·(-5)·1
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-6}{2*-5}=\frac{-2}{-10}
=1/5
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+6}{2*-5}=\frac{10}{-10}
=-1
$