9b^2-9b-40=0

Solution for 9b^2-9b-40=0 equation:

9b^2-9b-40=0

a = 9; b = -9; c = -40;
Δ = b2-4ac
Δ = -92-4·9·(-40)
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-39}{2*9}=\frac{-30}{18}
=-1+2/3
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+39}{2*9}=\frac{48}{18}
=2+2/3
$