b^2+3b=108

Solution for b^2+3b=108 equation:

b^2+3b=108

We move all terms to the left:

b^2+3b-(108)=0

a = 1; b = 3; c = -108;
Δ = b2-4ac
Δ = 32-4·1·(-108)
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-21}{2*1}=\frac{-24}{2}
=-12
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+21}{2*1}=\frac{18}{2}
=9
$