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Maxima of discrete functions involving nPr, nCr, etc?

  1. May 6, 2016 #1
    1. The problem statement, all variables and given/known data

    So I want to prove that the expression 20Cr×0.1r 0.9(20-r) reaches maximum value for r=(0.1)×20=2
    2. Relevant equations

    3. The attempt at a solution
    I can prove it by trial and error but can't differentiate the expression because nCr isn't continuous.
  2. jcsd
  3. May 6, 2016 #2
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