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b | (a-1), (2a+1) | (5b-3), a>1

Source: Greece Junior Math Olympiad 2023 p4

March 2, 2024
number theoryDivisorsdivides

Problem Statement

Find all positive integers a,ba,b with a>1a>1 such that, bb is a divisor of a1a-1 and 2a+12a+1 is a divisor of 5b35b-3.