0=2x^2-12x-240

Solution for 0=2x^2-12x-240 equation:

0=2x^2-12x-240

We move all terms to the left:

0-(2x^2-12x-240)=0

We add all the numbers together, and all the variables

-(2x^2-12x-240)=0

We get rid of parentheses

-2x^2+12x+240=0

a = -2; b = 12; c = +240;
Δ = b2-4ac
Δ = 122-4·(-2)·240
Δ = 2064
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2064}=\sqrt{16*129}=\sqrt{16}*\sqrt{129}=4\sqrt{129}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{129}}{2*-2}=\frac{-12-4\sqrt{129}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{129}}{2*-2}=\frac{-12+4\sqrt{129}}{-4}
$