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Homework Help: How to show this mathmatically?

  1. Sep 30, 2011 #1
    1. The problem statement, all variables and given/known data

    Let A and B be sets.
    Show that A \ B = ∅ if and only if A ⊆ B.

    I think this means that A is a subset of B, therefor if I remove all the elements of A that are in B, A would end up being empty (or ∅).

    How do I write this mathmatically or is the above sentence acceptable?
  2. jcsd
  3. Sep 30, 2011 #2
    You would start with something like, A is a subset of B implies for all x in A, x is in B. ...
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