-3b(b+10)=9

Solution for -3b(b+10)=9 equation:

-3b(b+10)=9

We move all terms to the left:

-3b(b+10)-(9)=0

We multiply parentheses

-3b^2-30b-9=0

a = -3; b = -30; c = -9;
Δ = b2-4ac
Δ = -302-4·(-3)·(-9)
Δ = 792
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:

$\sqrt{\Delta}=\sqrt{792}=\sqrt{36*22}=\sqrt{36}*\sqrt{22}=6\sqrt{22}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-6\sqrt{22}}{2*-3}=\frac{30-6\sqrt{22}}{-6}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+6\sqrt{22}}{2*-3}=\frac{30+6\sqrt{22}}{-6}
$