In order to solve $ \color{blue}{ 243x^{9}+324x^{8}+162x^{6} = 0 } $, first we need to factor our $ x^6 $.
$$ 243x^{9}+324x^{8}+162x^{6} = x^6 \left( 243x^{3}+324x^{2}+162 \right) $$$ x = 0 $ is a root of multiplicity $ 6 $.
The remaining roots can be found by solving equation $ 243x^{3}+324x^{2}+162 = 0$.
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using qubic formulas.