$$9x^4-8x^3-10 = 0$$
Answer
$$ \begin{matrix}x_1 = -0.85972 & x_2 = 1.34527 & x_3 = 0.20167+0.95919i \\[1 em] x_4 = 0.20167-0.95919i & \\[1 em] \end{matrix} $$
Explanation
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using quartic formulas
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