$$3x^4+4x-8 = 0$$
Answer
$$ \begin{matrix}x_1 = 1.0585 & x_2 = -1.46622 & x_3 = 0.20386+1.29486i \\[1 em] x_4 = 0.20386-1.29486i & \\[1 em] \end{matrix} $$
Explanation
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using quartic formulas
This page was created using
Polynomial Equations Solver