Use the results of exercises 1 and 2 to prove that a union
Chapter 7, Problem 31E(choose chapter or problem)
Use the results of exercises 1 and 2 to prove that a union of any two countable sets is countable.Exercise 1Prove that a disjoint union of any finite set and any countably infinite set is countably infinite.Exercise 2Prove that a union of any two countably infinite sets is countably infinite.
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