4: \textbf{Proof} Prove that if $A$ and $B$ are countable sets, then $A \cup B$ is...

4: \textbf{Proof} Prove that if $A$ and $B$ are countable sets, then $A \cup B$ is countable.

5: Use induction and problem 4 to prove that if $A_1, A_2, ..., A_m$ are each countable sets, then the union $A_1 \cup A_2 \cup ... \cup A_m$ is countable.

#5 please

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Colby Messinger answered 1 year ago

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