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Homework Help: Infinite limits

  1. Feb 17, 2008 #1
    1. The problem statement, all variables and given/known data

    Give a definition to explain what it means if the limit of Xn as n->infinity is itself equal to infinity.

    2. Relevant equations

    3. The attempt at a solution

    It seems the typical use of epsilon to show limits (that we approach arbitrary closeness) doesn't work here, so I had thought I could say it is the opposite of being bounded, but I'm not sure about how to say this more formally...

    Thanks for any ideas you may be able to offer
  2. jcsd
  3. Feb 17, 2008 #2

    Well you mention the idea of "arbitrary closeness" using the epsilon definition. Why not think about it in terms of the arbitrary "largeness" of xn as n becomes large?
    Or try to use epsilon in reverse?
  4. Feb 17, 2008 #3


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    Science Advisor

    The "the typical use of epsilon to show limits " works fine. It is the "delta" that doesn't work! Saying that a number is "going to infinity" does mean that it is unbounded so instead of "[itex]|x- a|< \delta[/itex]" as you would with "limit as x goes to a", how about something like "x> N" for some number N.
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