I'm once again having issues solving an inequality. Any assistance would be much appreciated

$\displaystyle x^3-2x^2-9x-2 >= -20$

I can't simplify by grouping, as that results in

$\displaystyle x^2(x-2) + (-9x-2) >= -20$ which lacks a common term

and as far as I can tell, this isn't a difference or sum of cubes, so how are the critical points calculated?