I don't see how this is the case. Let a(adsbygoogle = window.adsbygoogle || []).push({}); _{o}and b_{o}be members of [A,B] with a_{o}<b_{o}. Let {a_{i}} be a strictly decreasing sequence, with each a_{i}>A and {b_{i}} be a strictly increasing sequencing with each b_{i}<B. Let the limits of the two sequences be A and B, respectively. Then define I_{i}= [a_{i},b_{i}]. It seems to me that the union of {I_{i}} is an open set, not a closed set. Thoughts?

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# The union of any collection of closed sets is closed?

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