(adsbygoogle = window.adsbygoogle || []).push({}); 1. What are all the open subsets of the subspace Z of R.

2. Relevant equations: def of openness

3. I think the solution is all the subsets of Z, but I can't see how, for example you can say the subset of Z: {1} has a B(1,r) with r>0 is contained in {1}.

Thanks for any help.

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# Openness of subsets of the integers.

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