p^2-p+0,21=0

Solution for p^2-p+0,21=0 equation:

p^2-p+0.21=0

We add all the numbers together, and all the variables

p^2-1p+0.21=0

a = 1; b = -1; c = +0.21;
Δ = b2-4ac
Δ = -12-4·1·0.21
Δ = 0.16
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)-\sqrt{0.16}}{2*1}=\frac{1-\sqrt{0.16}}{2}
$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{0.16}}{2*1}=\frac{1+\sqrt{0.16}}{2}
$