$$x^8-34x^4+225 = 0$$
Answer
$$ \begin{matrix}x_1 = 1.73205 & x_2 = -1.73205 & x_3 = 2.23607 \\[1 em] x_4 = -2.23607 & x_5 = 1.73205i & x_6 = -1.73205i \\[1 em] x_7 = 2.23607i & x_8 = -2.23607i \\[1 em] \end{matrix} $$
Explanation
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using Newton method.
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