3x(4x-40)=360

Solution for 3x(4x-40)=360 equation:

3x(4x-40)=360

We move all terms to the left:

3x(4x-40)-(360)=0

We multiply parentheses

12x^2-120x-360=0

a = 12; b = -120; c = -360;
Δ = b2-4ac
Δ = -1202-4·12·(-360)
Δ = 31680
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:

$\sqrt{\Delta}=\sqrt{31680}=\sqrt{576*55}=\sqrt{576}*\sqrt{55}=24\sqrt{55}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-120)-24\sqrt{55}}{2*12}=\frac{120-24\sqrt{55}}{24}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-120)+24\sqrt{55}}{2*12}=\frac{120+24\sqrt{55}}{24}
$