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Math Help - Set Theory Problems (please help)

  1. #1
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    Angry Set Theory Problems (please help)

    1. Prove that if A U B = A and A intersect B = A then A = B

    2. Show that is general (A-B) U B is not A

    3. Let A = {2,4,...,2n} and B = {3,6,...,3n}. Find A-B
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  2. #2
    Senior Member vincisonfire's Avatar
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    1. A \cup B = A \implies B \subseteq A
     A \cap B = A \implies A \subseteq B
    It follows that ...
    2. Let A = \{1,2,3\}, B=\{1,2,3,4\} then  (A \backslash B) \cup B \neq A
    It is true if  B \subseteq A
    3. Take out multiples of 6.
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