3x(2x+2)=72

Solution for 3x(2x+2)=72 equation:

3x(2x+2)=72

We move all terms to the left:

3x(2x+2)-(72)=0

We multiply parentheses

6x^2+6x-72=0

a = 6; b = 6; c = -72;
Δ = b2-4ac
Δ = 62-4·6·(-72)
Δ = 1764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1764}=42$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-42}{2*6}=\frac{-48}{12}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+42}{2*6}=\frac{36}{12}
=3
$