x^2-1.8*x-0.09=0

Solution for x^2-1.8*x-0.09=0 equation:

x^2-1.8x-0.09=0

a = 1; b = -1.8; c = -0.09;
Δ = b2-4ac
Δ = -1.82-4·1·(-0.09)
Δ = 3.6
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{-(-1.8)-\sqrt{3.6}}{2*1}=\frac{1.8-\sqrt{3.6}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.8)+\sqrt{3.6}}{2*1}=\frac{1.8+\sqrt{3.6}}{2}
$