$$-x^3+39x^2-369x+999 = 0$$
Answer
$$ \begin{matrix}x_1 = 5.07668 & x_2 = 7.42669 & x_3 = 26.49663 \end{matrix} $$
Explanation
This polynomial has no rational roots that can be found using Rational Root Test.
Roots were found using qubic formulas.
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Polynomial Equations Solver