A congruence relation (or simply congruence) is an equivalence relation.
Let a, b, m € Z and m ≥ 2. Then ‘a’ is said to be congruent to ‘b’ modulo m if m|(a – b) i.e., a ≡ b (mod m) ⇔ m|(a – b)
For a given positive integer n, two integers a and b are called congruent modulo.
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