120=2x^2-8x

Solution for 120=2x^2-8x equation:

120=2x^2-8x

We move all terms to the left:

120-(2x^2-8x)=0

We get rid of parentheses

-2x^2+8x+120=0

a = -2; b = 8; c = +120;
Δ = b2-4ac
Δ = 82-4·(-2)·120
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-32}{2*-2}=\frac{-40}{-4}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+32}{2*-2}=\frac{24}{-4}
=-6
$