Exercise 2.1.4 (First examples, part 4)

If an integer x is even, observe that it must satisfy the congruence x ≡ 0 ( mod 2 ) . If an integer y is odd, what congruence does it satisfy? What congruence does an integer z of the form 6 k + 1 satisfy?

Answers

Proof.

y  is odd  ⟺ ∃ ⁡ k ∈ ℤ , y = 2 k + 1 ⟺ y ≡ 1 ( mod 2 ) . ∃ ⁡ k ∈ ℤ , z = 6 k + 1 ⟺ z ≡ 1 ( mod 6 ) . □
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2024-08-21 10:01
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