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Math Help - Finding the zeros

  1. #1
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    Finding the zeros

    have a polynomial that I need to find the zeros but I just want to know if I am going about it the correct way:

    F(x)=x^4-3x^3-9x^2+27x

    What I did was factored by grouping to get:

    x^3(x-3)-9x(x-3)

    (x-3)(x^3-9x) <<here i factored out an x to get x(x^2-9) and then i found the zero to be 3 for both. Is this correct? Any help is greatly appreciated
    Last edited by nascar77; September 15th 2009 at 05:49 PM. Reason: I found the answer myself. Thanks anyways!
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  2. #2
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    Quote Originally Posted by nascar77 View Post
    have a polynomial that I need to find the zeros but I just want to know if I am going about it the correct way:

    F(x)=x^4-3x^3-9x^2+27x

    What I did was factored by grouping to get:

    x^3(x-3)-9x(x-3)

    (x-3)(x^3-9x) <<here i factored out an x to get x(x^2-9) and then i found the zero to be 3 for both. Is this correct? Any help is greatly appreciated
    x^2 - 9 = (x - 3)(x + 3)
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  3. #3
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    In addition to the new root mr. fantastic pointed out, there is a third, obvious one. Remember the factor of "x". This polynomial has three distince zeroes.
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