Exercise 2.2.4 (First examples, part 4)

The fact that the product of any three consecutive integers is divisible by 3 leads to the identical congruence x ( x + 1 ) ( x + 2 ) ≡ 0 ( mod 3 ) . Generalise this, and write an identical congruence modulo m .

Answers

Proof. Since the product of any m consecutive integers is divisible by m , we obtain, for all x ∈ ℤ ,

x ( x + 1 ) ⋯ ( x + m − 1 ) ≡ 0 ( mod m ) .

We can also write

x ( x − 1 ) ⋯ ( x − ( m − 1 ) ) ≡ 0 ( mod m ) .

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2024-08-18 16:07
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