78=3x*2x

Solution for 78=3x*2x equation:

78=3x*2x

We move all terms to the left:

78-(3x*2x)=0

We add all the numbers together, and all the variables

-(+3x*2x)+78=0

We get rid of parentheses

-3x*2x+78=0

Wy multiply elements

-6x^2+78=0

a = -6; b = 0; c = +78;
Δ = b2-4ac
Δ = 02-4·(-6)·78
Δ = 1872
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:

$\sqrt{\Delta}=\sqrt{1872}=\sqrt{144*13}=\sqrt{144}*\sqrt{13}=12\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12\sqrt{13}}{2*-6}=\frac{0-12\sqrt{13}}{-12}
=-\frac{12\sqrt{13}}{-12}
=-\frac{\sqrt{13}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12\sqrt{13}}{2*-6}=\frac{0+12\sqrt{13}}{-12}
=\frac{12\sqrt{13}}{-12}
=\frac{\sqrt{13}}{-1}
$