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Thread: Composite Expression

  1. December 23rd 2008, 05:51 AM #1
    Winding Function
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    Composite Expression

    How I can tell that 4k^3+18k^2+28k+15 is composite for an positive integer n?

    Thanks!
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  2. December 23rd 2008, 06:58 AM #2
    TwistedOne151
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    Factoring

    Consider that 4k^3+18k^2+28k+15=(2k+3)(2k^2+6k+5).

    --Kevin C.
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  3. December 23rd 2008, 06:58 AM #3
    Isomorphism
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    But where is 'n' in the expression?

    I had to do a fair amount trial and error to figure out the following factorization:

    4k^3+18k^2+28k+15 = (2k+3)(2k^2 + 6k + 5)
    Last edited by Isomorphism; December 23rd 2008 at 07:04 AM. Reason: Got beaten by the TwistedOne!
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