72=3x^2-6x

Solution for 72=3x^2-6x equation:

72=3x^2-6x

We move all terms to the left:

72-(3x^2-6x)=0

We get rid of parentheses

-3x^2+6x+72=0

a = -3; b = 6; c = +72;
Δ = b2-4ac
Δ = 62-4·(-3)·72
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-30}{2*-3}=\frac{-36}{-6}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+30}{2*-3}=\frac{24}{-6}
=-4
$