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I need to prove that the following sets are countably infinite:
Re: Countably Infinite
Are you allowed to use that the rationals are countably infinite? Are you allowed to use that the union between two countably infinite sets is countably infinite? Are you allowed to use that a subset of a countably infinite set is countably infinite (or countably finite)?
"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."