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Math Help - Need help with a subset proof

  1. #1
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    Need help with a subset proof

    Here's the problem:

    Let X and Y be sets. Let f: X --> Y, and let A be a subset of Y.
    Prove that f(f-1(A)) is a subset of A.

    Any help is much appreciated!
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  2. #2
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    Re: Need help with a subset proof

    Quote Originally Posted by widenerl194 View Post
    Let X and Y be sets. Let f: X --> Y, and let A be a subset of Y.
    Prove that f(f-1(A)) is a subset of A.
    Can you describe what f(f^{-1}(A)) looks like in set-theoretic terms?
    If not, there is a place for you to begin,
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  3. #3
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    Re: Need help with a subset proof

    I think it might be

    f(f^-1(A)) = f(x) is an element of X such that f(x) is an element of f(A).
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