In order to solve $ \color{blue}{ 9x^{6}-3x^{4}+12x^{3}+11x = 0 } $, first we need to factor our $ x $.
$$ 9x^{6}-3x^{4}+12x^{3}+11x = x \left( 9x^{5}-3x^{3}+12x^{2}+11 \right) $$$ x = 0 $ is a root of multiplicity $ 1 $.
The remaining roots can be found by solving equation $ 9x^{5}-3x^{3}+12x^{2}+11 = 0$.
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using Newton method.