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Math Help - Recursion (and sets)

  1. #1
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    Dec 2011
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    Smile Recursion (and sets)

    I've been looking at this problem for ages and still can't work out what to do so help would be much appreciated!

    Problem:
    Set A is defined recursively. Find four elements in Set A.
    2 ∈ A
    x, y ∈ A, then x*y ∈ A (multiplication)


    [I thought a clause may have been missing, but not entirely sure.. recursion isn't a strong point of mine..]

    Thanks!
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  2. #2
    Junior Member
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    Sep 2011
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    Re: Recursion (and sets)

    Since 2 is in A, 2*2 = 4 must be in A. Since 4 and 2 are in A... can you take it from here?
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  3. #3
    Newbie
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    Re: Recursion (and sets)

    I didn't realise it was as easy as that.. Thank You!

    Would the next one be 4*2 = 8 is in A?
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  4. #4
    Junior Member
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    Re: Recursion (and sets)

    yep
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