6=-0.8x^2+3.2x+6

Solution for 6=-0.8x^2+3.2x+6 equation:

6=-0.8x^2+3.2x+6

We move all terms to the left:

6-(-0.8x^2+3.2x+6)=0

We get rid of parentheses

0.8x^2-3.2x-6+6=0

We add all the numbers together, and all the variables

0.8x^2-3.2x=0

a = 0.8; b = -3.2; c = 0;
Δ = b2-4ac
Δ = -3.22-4·0.8·0
Δ = 10.24
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{-(-3.2)-\sqrt{10.24}}{2*0.8}=\frac{3.2-\sqrt{10.24}}{1.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.2)+\sqrt{10.24}}{2*0.8}=\frac{3.2+\sqrt{10.24}}{1.6}
$