$$-x^3+3x+8 = 0$$
Answer
$$ \begin{matrix}x_1 = 2.49203 & x_2 = -1.24602+1.28751i & x_3 = -1.24602-1.28751i \end{matrix} $$
Explanation
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using qubic formulas.
This page was created using
Polynomial Equations Solver