Recent content by judelaw

Ah okay. I got it! I misunderstood "countable subsets. " Thank you micromass and disregardthat! And I just found a new website to frequent. :biggrin:

haha, like all of them? I'm not really sure what countable subsets of X means. I sort of understand the definition of countable (exists a bijection between it and the set of natural numbers?), but I don't really know how to relate that to this problem.

Let X be any infinite set. The countable closed topology is defined to be the topology having as its closed sets X and all countable subsets of X. Prove that this is indeed a topology on X. Any help would be greatly appreciated. Thanks!