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-   -   Permutations in math (https://www.askmehelpdesk.com/showthread.php?t=84487)

  • Apr 19, 2007, 11:05 PM
    sholman
    permutations in math
    I need to know how to solve this problem, I've been stuck for an hour, please help
    Question: find the indicated value of xCx-1 (it's a permutation)
  • Apr 20, 2007, 11:37 AM
    asterisk_man
    xCy would mean x Choose y and you're asking for xCx or x Choose x.



    so if we do xCx-1 we get:


    note: 0!=1 Math Forum - Ask Dr. Math

    If you think about it, this makes sense because it's like saying, how many ways are there to choose x items from a group of x items. The answer is 1, choose them all.

    I hope this helps and is what you were asking about.

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