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Homework Help: Function notation

  1. Jun 14, 2010 #1
    1. The problem statement, all variables and given/known data
    Give an example of a map from the set N of positive integers to itself which
    is surjective but not injective.


    2. Relevant equations



    3. The attempt at a solution
    It's easy to come up with an example, but I'm not sure on notation.
    Here's how I've written it, but I know it's not quite right. I'm sure you can see the function that I am meaning to give. Any help with the notation would be appreciated. If it's not clear what function I mean, let me know and I will put it into words :)

    [tex]\lbrace f:f(1)=1, f(s)=s-1,s>1\rbrace[/tex]
     
  2. jcsd
  3. Jun 14, 2010 #2

    Dick

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    That's plenty clear enough. Just defining f(1)=1 and f(s)=s-1 for s>1 without using the {} notation is also fine.
     
  4. Jun 14, 2010 #3
    Oh cool. Thank you for your quick response. I may actually just define the function as you say and use words to explain it if it comes up in the exam. I think the lecturer prefers things explained as much in words as possible anyway.
     
  5. Jun 14, 2010 #4

    Dick

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    Science Advisor
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    That's plenty clear enough. Just defining f(1)=1 and f(s)=s-1 for s>1 without using the {} notation is also fine.
     
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