0.81x2+-0.9x+1=0

Solution for 0.81x2+-0.9x+1=0 equation:

0.81x^2+-0.9x+1=0

We add all the numbers together, and all the variables

0.81x^2-0.9x=0

a = 0.81; b = -0.9; c = 0;
Δ = b2-4ac
Δ = -0.92-4·0.81·0
Δ = 0.81
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{-(-0.9)-\sqrt{0.81}}{2*0.81}=\frac{0.9-\sqrt{0.81}}{1.62}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.9)+\sqrt{0.81}}{2*0.81}=\frac{0.9+\sqrt{0.81}}{1.62}
$