0=18x^2-18x-108

Solution for 0=18x^2-18x-108 equation:

0=18x^2-18x-108

We move all terms to the left:

0-(18x^2-18x-108)=0

We add all the numbers together, and all the variables

-(18x^2-18x-108)=0

We get rid of parentheses

-18x^2+18x+108=0

a = -18; b = 18; c = +108;
Δ = b2-4ac
Δ = 182-4·(-18)·108
Δ = 8100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8100}=90$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-90}{2*-18}=\frac{-108}{-36}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+90}{2*-18}=\frac{72}{-36}
=-2
$