9b^2-30b-20=0

Solution for 9b^2-30b-20=0 equation:

9b^2-30b-20=0

a = 9; b = -30; c = -20;
Δ = b2-4ac
Δ = -302-4·9·(-20)
Δ = 1620
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:

$\sqrt{\Delta}=\sqrt{1620}=\sqrt{324*5}=\sqrt{324}*\sqrt{5}=18\sqrt{5}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-18\sqrt{5}}{2*9}=\frac{30-18\sqrt{5}}{18}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+18\sqrt{5}}{2*9}=\frac{30+18\sqrt{5}}{18}
$