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Homework Help: Countable Sets

  1. Apr 29, 2010 #1
    F is all integers that are multiplies of 5

    [tex]f(n) =
    \begin{cases}
    0, & \mbox{if }n\mbox{ 1} \\
    \frac{5n}{2}, & \mbox{if }n\mbox{ is even}\\
    ? , & \mbox{if }n\mbox{ is odd}
    \end{cases}
    [/tex]

    N exists in the natural number
    I don't know how to obtain the function that will represent the odd integers.
     
    Last edited: Apr 30, 2010
  2. jcsd
  3. Apr 30, 2010 #2

    Gib Z

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    Homework Helper

    Are you trying to get a function that produces all the integer multiples of 5?

    Whats wrong with f(n) = 5n ?
     
  4. Apr 30, 2010 #3
    I forgot to mention n exists in the natural numbers.
     
  5. Apr 30, 2010 #4

    Gib Z

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    Homework Helper

    Ok then, the n is even part of your function will give all the positive multiples, now try something similar for n odd. I don't know how to give you a decent hint without giving it away, but basically, the odd case is very similar to the even case, except with a negative sign, and a little change to the n term to make sure it's divisible by 2.
     
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