(x*2)x=800

Solution for (x*2)x=800 equation:

(x*2)x=800

We move all terms to the left:

(x*2)x-(800)=0

We add all the numbers together, and all the variables

(+x*2)x-800=0

We multiply parentheses

2x^2-800=0

a = 2; b = 0; c = -800;
Δ = b2-4ac
Δ = 02-4·2·(-800)
Δ = 6400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6400}=80$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-80}{2*2}=\frac{-80}{4}
=-20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+80}{2*2}=\frac{80}{4}
=20
$