0.8=1.6x+x^2

Solution for 0.8=1.6x+x^2 equation:

0.8=1.6x+x^2

We move all terms to the left:

0.8-(1.6x+x^2)=0

We get rid of parentheses

-x^2-1.6x+0.8=0

We add all the numbers together, and all the variables

-1x^2-1.6x+0.8=0

a = -1; b = -1.6; c = +0.8;
Δ = b2-4ac
Δ = -1.62-4·(-1)·0.8
Δ = 5.76
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{-(-1.6)-\sqrt{5.76}}{2*-1}=\frac{1.6-\sqrt{5.76}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.6)+\sqrt{5.76}}{2*-1}=\frac{1.6+\sqrt{5.76}}{-2}
$