In order to solve $ \color{blue}{ 4x^{14}-10x^{10}-20x^{9} = 0 } $, first we need to factor our $ x^9 $.
$$ 4x^{14}-10x^{10}-20x^{9} = x^9 \left( 4x^{5}-10x-20 \right) $$$ x = 0 $ is a root of multiplicity $ 9 $.
The remaining roots can be found by solving equation $ 4x^{5}-10x-20 = 0$.
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using Newton method.