Hello, thanks for reading.
Let (X,T) be a topologic space.
I got the next definition of "the closure of A, partial to X":
cl(A) = intersection (F | A is partial to F, F is closed in (X,T) )
I need to prove that cl(A) = AUA', where A' is the set of all accumulation points of A.
And aI don't succeed :-\