3.2=x^2-0.4x

Solution for 3.2=x^2-0.4x equation:

3.2=x^2-0.4x

We move all terms to the left:

3.2-(x^2-0.4x)=0

We get rid of parentheses

-x^2+0.4x+3.2=0

We add all the numbers together, and all the variables

-1x^2+0.4x+3.2=0

a = -1; b = 0.4; c = +3.2;
Δ = b2-4ac
Δ = 0.42-4·(-1)·3.2
Δ = 12.96
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{-(0.4)-\sqrt{12.96}}{2*-1}=\frac{-0.4-\sqrt{12.96}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.4)+\sqrt{12.96}}{2*-1}=\frac{-0.4+\sqrt{12.96}}{-2}
$