# Topology question closures

Long2024
If A and B are two non-closed subsets of X, how would one prove that the closure of A union B= the closure of A union closure of B? Also, what site would you recommend I download TeX from when I get my new computer (Dell, runs on windows)?

Staff Emeritus
And don't forget that, for sets, A = B means the same thing as $A \subseteq B \wedge B \subseteq A$.