2,6=20-x^2+2x

Solution for 2,6=20-x^2+2x equation:

2.6=20-x^2+2x

We move all terms to the left:

2.6-(20-x^2+2x)=0

We get rid of parentheses

x^2-2x-20+2.6=0

We add all the numbers together, and all the variables

x^2-2x-17.4=0

a = 1; b = -2; c = -17.4;
Δ = b2-4ac
Δ = -22-4·1·(-17.4)
Δ = 73.6
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{73.6}}{2*1}=\frac{2-\sqrt{73.6}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{73.6}}{2*1}=\frac{2+\sqrt{73.6}}{2}
$