Paper 1, Section I, F

Topics in Analysis
Part II, 2010

Let (X,d)(X, d) be a non-empty complete metric space with no isolated points, GG an open dense subset of XX and EE a countable dense subset of XX.

(i) Stating clearly any standard theorem you use, prove that G\EG \backslash E is a dense subset of XX.

(ii) If GG is only assumed to be uncountable and dense in XX, does it still follow that G\EG \backslash E is dense in XX ? Justify your answer.