$$3p^4+29p+56 = 0$$
Answer
$$ \begin{matrix}p_1 = 1.51735+1.97359i & p_2 = 1.51735-1.97359i & p_3 = -1.51735+0.84242i \\[1 em] p_4 = -1.51735-0.84242i & \\[1 em] \end{matrix} $$
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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