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Unformatted text preview: can’t order? 5. Let A = n m n ∈ Q ± ± ± 7-n o . (i) List three elements of A . (ii) List three rational numbers that don’t belong to A . (ii) Prove that A is closed under addition and closed under multiplication. 6. True or false? Explain. (i) ∀ n ∈ N , ∃ prime p such that p | n . (ii) ∃ prime p such that ∀ n ∈ N , p | n . 7. Determine whether the function f : N × N → N is one-to-one. (i) f ( n,m ) = 2 m 6 n (ii) f ( n,m ) = 36 m 6 n 1 2...
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- Spring '08
- Integers, Prime number, general proof, explicit counterexample