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Math Help - Factorising another polynomial over C

  1. #1
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    Factorising another polynomial over C

    Hi there

    I have a start on this polynomial:
     f(z) = x^4 - 2z^2 - 16z - 15
    If I let f(z) = f(-1) I will find that the expression equals zero and so (z+1) is a factor.
    But where do I go from here?

    The answer in the back of the book is (z+1)(z+1+2i)(z+1-2i)(z-3)

    cheers
    David.
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  2. #2
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    I assume the function is actually \displaystyle f(z) = z^4 - 2z^2 - 16z - 15.

    Since you've found a factor, long divide to get the cubic factor. See if you can factorise that cubic.
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