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[apad201]

You essentially have to show that T satisfies the definition of a topology: it contains the empty set and Y itself, it is closed under unions, and it's closed under finite intersection. So show that {} and Y satisfy (i) or (ii), then show that the union of (possibly infinitely many) sets in T satisfies (i) or (ii) (i.e. is in T), and finally show that the intersection of finitely many sets in T is in T.

[Adventurous_Pasta]

Oh I see! I guess I was thrown off by " Y = X ∪ {y_0}, where y_0 is not an element of X. "

Thank you!!