0=1+2n-0.2n^2

Solution for 0=1+2n-0.2n^2 equation:

0=1+2n-0.2n^2

We move all terms to the left:

0-(1+2n-0.2n^2)=0

We add all the numbers together, and all the variables

-(1+2n-0.2n^2)=0

We get rid of parentheses

0.2n^2-2n-1=0

a = 0.2; b = -2; c = -1;
Δ = b2-4ac
Δ = -22-4·0.2·(-1)
Δ = 4.8
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-\sqrt{4.8}}{2*0.2}=\frac{2-\sqrt{4.8}}{0.4}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+\sqrt{4.8}}{2*0.2}=\frac{2+\sqrt{4.8}}{0.4}
$