x*(x*2)=648

Solution for x*(x*2)=648 equation:

x(x*2)=648

We move all terms to the left:

x(x*2)-(648)=0

We add all the numbers together, and all the variables

x(+x*2)-648=0

We multiply parentheses

2x^2-648=0

a = 2; b = 0; c = -648;
Δ = b2-4ac
Δ = 02-4·2·(-648)
Δ = 5184
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5184}=72$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-72}{2*2}=\frac{-72}{4}
=-18
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+72}{2*2}=\frac{72}{4}
=18
$