MethodMath
FT
May 16, 2026

How to factor polynomials of degree 3 or higher efficiently?

I can factor quadratics easily, but I struggle with cubic and quartic polynomials. For example:

x36x2+11x6=0x^3 - 6x^2 + 11x - 6 = 0

What strategies exist beyond the rational root theorem? Are there efficient methods for spotting factorizations? Also, what about:

x45x3+6x2+4x8=0x^4 - 5x^3 + 6x^2 + 4x - 8 = 0

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1 Answer

PJ
Prof. James ChenMay 16, 2026 Accepted
For $x^3 - 6x^2 + 11x - 6 = 0$, the rational root theorem suggests testing $\pm 1, \pm 2, \pm 3, \pm 6$. We find $x = 1$ works: $1 - 6 + 11 - 6 = 0$. Then use synthetic division: $$\begin{array}{r|rrrr} 1 & 1 & -6 & 11 & -6 \\ & \downarrow & 1 & -5 & 6 \\ \hline & 1 & -5 & 6 & 0 \end{array}$$ So $(x - 1)(x^2 - 5x + 6) = (x - 1)(x - 2)(x - 3) = 0$, giving $x = 1, 2, 3$. **General strategies for higher-degree polynomials:** 1. Rational root theorem to find first root 2. Synthetic division to reduce degree 3. For quartics, look for quadratic in disguise (e.g., $x^4 - 5x^2 + 6 = 0$) 4. Grouping terms (e.g., $x^3 + 3x^2 + 3x + 1 = (x+1)^3$) 5. Difference/sum of cubes: $a^3 \pm b^3 = (a \pm b)(a^2 \mp ab + b^2)$
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