$$x^4+20x+100 = 0$$
Answer
$$ \begin{matrix}x_1 = 2.26287+2.70743i & x_2 = 2.26287-2.70743i & x_3 = -2.26287+1.70617i \\[1 em] x_4 = -2.26287-1.70617i & \\[1 em] \end{matrix} $$
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