120=3x*x

Solution for 120=3x*x equation:

120=3x*x

We move all terms to the left:

120-(3x*x)=0

We add all the numbers together, and all the variables

-(+3x*x)+120=0

We get rid of parentheses

-3x*x+120=0

Wy multiply elements

-3x^2+120=0

a = -3; b = 0; c = +120;
Δ = b2-4ac
Δ = 02-4·(-3)·120
Δ = 1440
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:

$\sqrt{\Delta}=\sqrt{1440}=\sqrt{144*10}=\sqrt{144}*\sqrt{10}=12\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12\sqrt{10}}{2*-3}=\frac{0-12\sqrt{10}}{-6}
=-\frac{12\sqrt{10}}{-6}
=-\frac{2\sqrt{10}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12\sqrt{10}}{2*-3}=\frac{0+12\sqrt{10}}{-6}
=\frac{12\sqrt{10}}{-6}
=\frac{2\sqrt{10}}{-1}
$