$$4x^3-12x-x+3 = 0$$
Answer
$$ \begin{matrix}x_1 = 0.23475 & x_2 = 1.6739 & x_3 = -1.90865 \end{matrix} $$
Explanation
$$ \begin{aligned} 4x^3-12x-x+3 &= 0&& \text{simplify left side} \\[1 em]4x^3-13x+3 &= 0&& \\[1 em] \end{aligned} $$
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