2x^2+12x-6x-36=720

Solution for 2x^2+12x-6x-36=720 equation:

2x^2+12x-6x-36=720

We move all terms to the left:

2x^2+12x-6x-36-(720)=0

We add all the numbers together, and all the variables

2x^2+6x-756=0

a = 2; b = 6; c = -756;
Δ = b2-4ac
Δ = 62-4·2·(-756)
Δ = 6084
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6084}=78$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-78}{2*2}=\frac{-84}{4}
=-21
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+78}{2*2}=\frac{72}{4}
=18
$