x*x-0.2=640

Solution for x*x-0.2=640 equation:

x*x-0.2=640

We move all terms to the left:

x*x-0.2-(640)=0

We add all the numbers together, and all the variables

x*x-640.2=0

Wy multiply elements

x^2-640.2=0

a = 1; b = 0; c = -640.2;
Δ = b2-4ac
Δ = 02-4·1·(-640.2)
Δ = 2560.8
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{2560.8}}{2*1}=\frac{0-\sqrt{2560.8}}{2}
=-\frac{\sqrt{}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{2560.8}}{2*1}=\frac{0+\sqrt{2560.8}}{2}
=\frac{\sqrt{}}{2}
$