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Number of equivalent's solutions

Source: 2020 Turkey TST P9

March 14, 2020
number theory

Problem Statement

For a,na,n positive integers we show number of different integer 10-tuples (x1,x2,...,x10) (x_1,x_2,...,x_{10}) on (modn) (mod n) satistfying x1x2...x10=a(modn)x_1x_2...x_{10}=a (mod n) with f(a,n)f(a,n). Let a,ba,b given positive integers , a) Prove that there exist a positive integer cc such that for all nZ+n\in \mathbb{Z^+} f(a,cn)f(b,cn)\frac {f(a,cn)}{f(b,cn)}is constant b) Find all (a,b)(a,b) pairs such that minumum possible value of cc is 27 where cc satisfying condition in (a)(a)