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Math Help - How to Factor 3rd Degree (and Higher) Polynomials

  1. #1
    Junior Member masoug's Avatar
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    Question How to Factor 3rd Degree (and Higher) Polynomials

    Hi,
    What is the general method for factoring 3rd degree polynomials? Such as:
    9x^3+7x^2-3x+90=0

    Thanks!

    -Masoug
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  2. #2
    MHF Contributor
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    Use google; you'll get sites like:
    How to Factor Cube Functions | eHow.com
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  3. #3
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    The only "general method" for factoring polynomials, even quadratic polynomials, is to solve the equation. If x_1, x_2, ..., x_n are roots of ax^n+ bx^{n-1}+ \cdot\cdot\cdot+ yx+z= 0 then ax^n+ bx^{n-1}+ \cdot\cdot\cdot\+ z= a(x- x_1)(x- x_2)\cdot\cdot\cdot(x- x_n).

    Other than that, you do exactly the sort of thing you do for quadratics- look at the factors of the leading coefficient and constant term and try to distribute them among the factors.

    Of course, MOST polynomials, even quadratic polynomials, cannot be factored using only integer coefficients, which is what is usually understood by "factoring".
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