Cubic polynomials are polynomials of degree 3. Descartes' method to solving the roots of cubic functions is the same as that of solving the roots of quartic functions (polynomials with degree 4). Simply multiply the cubic polynomial through by x creating a quartic polynomial and then follow the steps to solving the roots of the quartic function (you can find that here). When you do this, ignore the x=0 solution. (Rubinstein, 4)
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