3x*3*3x=72

Solution for 3x*3*3x=72 equation:

3x*3*3x=72

We move all terms to the left:

3x*3*3x-(72)=0

Wy multiply elements

27x^2*3-72=0

Wy multiply elements

81x^2-72=0

a = 81; b = 0; c = -72;
Δ = b2-4ac
Δ = 02-4·81·(-72)
Δ = 23328
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:

$\sqrt{\Delta}=\sqrt{23328}=\sqrt{11664*2}=\sqrt{11664}*\sqrt{2}=108\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-108\sqrt{2}}{2*81}=\frac{0-108\sqrt{2}}{162}
=-\frac{108\sqrt{2}}{162}
=-\frac{2\sqrt{2}}{3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+108\sqrt{2}}{2*81}=\frac{0+108\sqrt{2}}{162}
=\frac{108\sqrt{2}}{162}
=\frac{2\sqrt{2}}{3}
$