x*x-0.9x+0.12=0

Solution for x*x-0.9x+0.12=0 equation:

x*x-0.9x+0.12=0

We add all the numbers together, and all the variables

-0.9x+x*x+0.12=0

Wy multiply elements

x^2-0.9x+0.12=0

a = 1; b = -0.9; c = +0.12;
Δ = b2-4ac
Δ = -0.92-4·1·0.12
Δ = 0.33
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{0.33}}{2*1}=\frac{0.9-\sqrt{0.33}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.9)+\sqrt{0.33}}{2*1}=\frac{0.9+\sqrt{0.33}}{2}
$