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  1. No.

  2. No.

  3. \(2\Z \cap 3\Z\) is the set of all integers which are multiples of both 2 and 3 (so multiples of 6). Therefore \(2\Z \cap 3\Z = \{x \in \Z \st \exists y\in \Z(x = 6y)\}\text{.}\)

  4. \(2\Z \cup 3\Z\text{.}\)

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