(18-2x)(12-2x)=72

Solution for (18-2x)(12-2x)=72 equation:

(18-2x)(12-2x)=72

We move all terms to the left:

(18-2x)(12-2x)-(72)=0

We add all the numbers together, and all the variables

(-2x+18)(-2x+12)-72=0

We multiply parentheses ..

(+4x^2-24x-36x+216)-72=0

We get rid of parentheses

4x^2-24x-36x+216-72=0

We add all the numbers together, and all the variables

4x^2-60x+144=0

a = 4; b = -60; c = +144;
Δ = b2-4ac
Δ = -602-4·4·144
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-36}{2*4}=\frac{24}{8}
=3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+36}{2*4}=\frac{96}{8}
=12
$