p^2=0.81p

Solution for p^2=0.81p equation:

p^2=0.81p

We move all terms to the left:

p^2-(0.81p)=0

We add all the numbers together, and all the variables

p^2-(+0.81p)=0

We get rid of parentheses

p^2-0.81p=0

a = 1; b = -0.81; c = 0;
Δ = b2-4ac
Δ = -0.812-4·1·0
Δ = 0.6561
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{-(-0.81)-\sqrt{0.6561}}{2*1}=\frac{0.81-\sqrt{0.6561}}{2}
$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.81)+\sqrt{0.6561}}{2*1}=\frac{0.81+\sqrt{0.6561}}{2}
$