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Combinatoric Problems, need help

  1. Mar 1, 2006 #1
    I need help on how to solve these homework problems.

    1. Coefficient of x^12 in (1+x^2)(1-x)^-10

    2.Find a generating function for the problem: there are 4 food categories, each category comprising of 20 distinct foods. Ten foods with at least one from each category is to be selected. how many menus are possible?
  2. jcsd
  3. Mar 1, 2006 #2

    matt grime

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    Science Advisor
    Homework Helper

    1. Just do it; you know the expansion of (1-x)^{-10} and that is all that you need.
  4. Mar 1, 2006 #3
    is the answer C(22,10)?
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