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Homework Help: Real Analysis: Sequences and Series

  1. Apr 13, 2010 #1
    Suppose that ak is a decreasing sequence and (ak) approaches 0. Prove that for every k in the natural numbers, ak is greater than or equal to 0.

    I was thinking I should assume the sequence is bounded below by 0 and do a proof by contradiction.

    Any suggestions?
  2. jcsd
  3. Apr 13, 2010 #2


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    If you assume the sequence is bounded below by 0 you are assuming what you are trying to prove.

    Just try an indirect argument. Assume some ak < 0. You should be able to get an easy contradiction.
  4. Apr 13, 2010 #3
    thanks. I guess I just really don't know what I'm doing.
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