Question:Let B1, B2, B3, . . . be a sequence of sets, each of which is...
Question
Let B1, B2, B3, . . . be a sequence of sets, each of which is...
Let B1, B2, B3, . . . be a sequence of sets, each of which is
countable. Prove that the union, A = S∞ n=1 Bn, of all of the sets
in the sequence is a countable set.