126=5x*3x

Solution for 126=5x*3x equation:

126=5x*3x

We move all terms to the left:

126-(5x*3x)=0

We add all the numbers together, and all the variables

-(+5x*3x)+126=0

We get rid of parentheses

-5x*3x+126=0

Wy multiply elements

-15x^2+126=0

a = -15; b = 0; c = +126;
Δ = b2-4ac
Δ = 02-4·(-15)·126
Δ = 7560
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:

$\sqrt{\Delta}=\sqrt{7560}=\sqrt{36*210}=\sqrt{36}*\sqrt{210}=6\sqrt{210}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{210}}{2*-15}=\frac{0-6\sqrt{210}}{-30}
=-\frac{6\sqrt{210}}{-30}
=-\frac{\sqrt{210}}{-5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{210}}{2*-15}=\frac{0+6\sqrt{210}}{-30}
=\frac{6\sqrt{210}}{-30}
=\frac{\sqrt{210}}{-5}
$