-x^2-18=9x

Solution for -x^2-18=9x equation:

-x^2-18=9x

We move all terms to the left:

-x^2-18-(9x)=0

We add all the numbers together, and all the variables

-1x^2-9x-18=0

a = -1; b = -9; c = -18;
Δ = b2-4ac
Δ = -92-4·(-1)·(-18)
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-3}{2*-1}=\frac{6}{-2}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+3}{2*-1}=\frac{12}{-2}
=-6
$