P(x)=2.1x-0.01x^2-1

Solution for P(x)=2.1x-0.01x^2-1 equation:

(P)=2.1P-0.01P^2-1

We move all terms to the left:

(P)-(2.1P-0.01P^2-1)=0

We get rid of parentheses

0.01P^2-2.1P+P+1=0

We add all the numbers together, and all the variables

0.01P^2-1.1P+1=0

a = 0.01; b = -1.1; c = +1;
Δ = b2-4ac
Δ = -1.12-4·0.01·1
Δ = 1.17
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1.1)-\sqrt{1.17}}{2*0.01}=\frac{1.1-\sqrt{1.17}}{0.02}
$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.1)+\sqrt{1.17}}{2*0.01}=\frac{1.1+\sqrt{1.17}}{0.02}
$