2x(x+4)=120

Solution for 2x(x+4)=120 equation:

2x(x+4)=120

We move all terms to the left:

2x(x+4)-(120)=0

We multiply 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
$