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

Solution for 8(b+3)(b-9)=0 equation:

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

We multiply parentheses ..

8(+b^2-9b+3b-27)=0

We multiply parentheses

8b^2-72b+24b-216=0

We add all the numbers together, and all the variables

8b^2-48b-216=0

a = 8; b = -48; c = -216;
Δ = b2-4ac
Δ = -482-4·8·(-216)
Δ = 9216
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9216}=96$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-48)-96}{2*8}=\frac{-48}{16}
=-3
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-48)+96}{2*8}=\frac{144}{16}
=9
$