0=2x^2+6x-36-720

Solution for 0=2x^2+6x-36-720 equation:

0=2x^2+6x-36-720

We move all terms to the left:

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

We add all the numbers together, and all the variables

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

We get rid of parentheses

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