x^2-2x=0.8

Solution for x^2-2x=0.8 equation:

x^2-2x=0.8

We move all terms to the left:

x^2-2x-(0.8)=0

We add all the numbers together, and all the variables

x^2-2x-0.8=0

a = 1; b = -2; c = -0.8;
Δ = b2-4ac
Δ = -22-4·1·(-0.8)
Δ = 7.2
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{-(-2)-\sqrt{7.2}}{2*1}=\frac{2-\sqrt{7.2}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{7.2}}{2*1}=\frac{2+\sqrt{7.2}}{2}
$