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Math Help - Find Accumulation points and Isolation points of set X, Y, Z and W in R^2

  1. #1
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    Find Accumulation points and Isolation points of set X, Y, Z and W in R^2

    1)
    X={(2a,2b) | a,b integers}

    2)
    Y={(p,q) | p,q rational}

    3)
    Z={(1/n,m/n) | m,n integers, n not equal 0}

    4)
    W={(1/n+1/m,1) | m,n integers, m and n not equal 0}

    Hope someone can help... very confused and struggling
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  2. #2
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    Re: Find Accumulation points and Isolation points of set X, Y, Z and W in R^2

    Do you know the definitions of "accumulation point" and "isolated point"?

    Have you drawn a picture of these sets?

    If you know the basic definitions (1) and (2), at least, should be easy.
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  3. #3
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    Re: Find Accumulation points and Isolation points of set X, Y, Z and W in R^2

    Hi HallsofIvy,

    Thank you for your reply. I read alot of the definitions in text and online and I'm not too sure if I have understood correctly. So for the 1st question. The set X is a set of even numbers right? So is acc(X) a set of even numbers?
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  4. #4
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    Re: Find Accumulation points and Isolation points of set X, Y, Z and W in R^2

    no, the first set is a set of *pairs* of even numbers. like a(n infinite) page of "dots" spaced 2 apart.
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