x^2+0.9x=-0.18

Solution for x^2+0.9x=-0.18 equation:

x^2+0.9x=-0.18

We move all terms to the left:

x^2+0.9x-(-0.18)=0

We add all the numbers together, and all the variables

x^2+0.9x+0.18=0

a = 1; b = 0.9; c = +0.18;
Δ = b2-4ac
Δ = 0.92-4·1·0.18
Δ = 0.09
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{0.09}}{2*1}=\frac{-0.9-\sqrt{0.09}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.9)+\sqrt{0.09}}{2*1}=\frac{-0.9+\sqrt{0.09}}{2}
$