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Homework Help: Binomial theorm

  1. Jul 14, 2006 #1
    Hello, everybody,

    I know how to get the first step, but I don't know how can the first step be changed to the format of the final answer, can anyone help?


    Attached Files:

  2. jcsd
  3. Jul 15, 2006 #2
    How many terms are in the product "(-4)(-5)...(-4-r+1)"? How can this product be combined with (-1)^r?

    Also, writing out r! as a product of consecutive integers should help.
  4. Jul 15, 2006 #3


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    Science Advisor

    Interesting! I was wondering how that r! in the denominator magically became 6.

    My suggestion (in fact what I did) is calculate both formulas for r= 1, 2, 3, 4, 5,... and see what happens.
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