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Thread: [SOLVED] Proving Combinations

  1. March 25th 2009, 02:35 PM #1
    DaCoo911
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    Exclamation [SOLVED] Proving Combinations

    I've been trying to prove this for quite some time today, I just can't seem to get my head around this one! O NO!


    C(k, r+1) = C(k, k-r-1)
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  2. March 25th 2009, 02:55 PM #2
    o_O
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    C(k, r+1) = \frac{k!}{(r+1)!(k - (r+1))!} = \frac{k!}{(r+1)!(k- r - 1)!}

    C(k, k-r-1) = \frac{k!}{(k-r-1)!(k - \left(k-r-1\right))!} = \cdots

    Can you show that the two are equal?
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