0.004=x^2-1.6x-0.8

Solution for 0.004=x^2-1.6x-0.8 equation:

0.004=x^2-1.6x-0.8

We move all terms to the left:

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

We get rid of parentheses

-x^2+1.6x+0.8+0.004=0

We add all the numbers together, and all the variables

-1x^2+1.6x+0.804=0

a = -1; b = 1.6; c = +0.804;
Δ = b2-4ac
Δ = 1.62-4·(-1)·0.804
Δ = 5.776
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{5.776}}{2*-1}=\frac{-1.6-\sqrt{5.776}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.6)+\sqrt{5.776}}{2*-1}=\frac{-1.6+\sqrt{5.776}}{-2}
$