In order to solve $ \color{blue}{ 36x^{6}+23x^{5}-3x^{4} = 0 } $, first we need to factor our $ x^4 $.
$$ 36x^{6}+23x^{5}-3x^{4} = x^4 \left( 36x^{2}+23x-3 \right) $$$ x = 0 $ is a root of multiplicity $ 4 $.
The remaining roots can be found by solving equation $ 36x^{2}+23x-3 = 0$.
$ 36x^{2}+23x-3 = 0 $ is a quadratic equation.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this equation.