5b^2-40b+2=0

Solution for 5b^2-40b+2=0 equation:

5b^2-40b+2=0

a = 5; b = -40; c = +2;
Δ = b2-4ac
Δ = -402-4·5·2
Δ = 1560
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:

$\sqrt{\Delta}=\sqrt{1560}=\sqrt{4*390}=\sqrt{4}*\sqrt{390}=2\sqrt{390}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-2\sqrt{390}}{2*5}=\frac{40-2\sqrt{390}}{10}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+2\sqrt{390}}{2*5}=\frac{40+2\sqrt{390}}{10}
$