(3x-18)(4x+12)=0

Solution for (3x-18)(4x+12)=0 equation:

(3x-18)(4x+12)=0

We multiply parentheses ..

(+12x^2+36x-72x-216)=0

We get rid of parentheses

12x^2+36x-72x-216=0

We add all the numbers together, and all the variables

12x^2-36x-216=0

a = 12; b = -36; c = -216;
Δ = b2-4ac
Δ = -362-4·12·(-216)
Δ = 11664
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{11664}=108$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-36)-108}{2*12}=\frac{-72}{24}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-36)+108}{2*12}=\frac{144}{24}
=6
$