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Factorial Question

  1. Jan 31, 2016 #1
    How do you get

    (n + 1)! = (n + 1)(n)(n - 1)(n - 2) ... 3 ⋅ 2 ⋅ 1

    ????

    Isn't (n + 1)! = (n + 1) ⋅ (n + 1 - 1) ⋅ (n + 1 - 2) ⋅ (n + 1 - 3) ⋅ (n + 1 - 4) ... and so on?
     
  2. jcsd
  3. Jan 31, 2016 #2

    Simon Bridge

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    You need to realise that:
    n+1-1 = n
    n+1-2 = n-1
    n+1-3 = n-2
    etc
     
  4. Jan 31, 2016 #3

    jedishrfu

    Staff: Mentor

    or more compactly:

    (n+1)! = (n+1) * (n+1-1)! = (n+1) * n!
     
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