0=1.8x+x^2

Solution for 0=1.8x+x^2 equation:

0=1.8x+x^2

We move all terms to the left:

0-(1.8x+x^2)=0

We add all the numbers together, and all the variables

-(1.8x+x^2)=0

We get rid of parentheses

-x^2-1.8x=0

We add all the numbers together, and all the variables

-1x^2-1.8x=0

a = -1; b = -1.8; c = 0;
Δ = b2-4ac
Δ = -1.82-4·(-1)·0
Δ = 3.24
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{3.24}}{2*-1}=\frac{1.8-\sqrt{3.24}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.8)+\sqrt{3.24}}{2*-1}=\frac{1.8+\sqrt{3.24}}{-2}
$