648=2x*x

Solution for 648=2x*x equation:

648=2x*x

We move all terms to the left:

648-(2x*x)=0

We add all the numbers together, and all the variables

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

We get rid of parentheses

-2x*x+648=0

Wy multiply elements

-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
$