$$-r^3+2r^2+12r-5 = 0$$
Answer
$$ \begin{matrix}r_1 = 0.39573 & r_2 = -2.8418 & r_3 = 4.44607 \end{matrix} $$
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