 Solution

ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2014/discrete-mathematics-continuous-mathematics-and-probability/3/b/i/solution

The notation means that

n

divides

a_{1} - a_{2}

a_{1} \equiv a_{2} (mod n) ⟺ there exists k \in Z with a_{1} - a_{2} = kn .

This is congruence modulo an integer; equivalently, the two integers have the same remainder on division by the positive integer

n

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