Olympiad prime

Find the number of solutions of the equation 2 p + 3 p = q n 2^p+3^p=q^n , where p p is a prime, and q q and n n are integers greater than 1.


The answer is 0.

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1 solution

Rajdeep Brahma
Jun 9, 2018

When p=2, q n q^n =13 which is impossible.Other wise p is odd and 5 divides 2 p + 3 p 2^p+3^p .Since n>1 we must have 25 dividing 2 p + 3 p 2^p+3^p .....interesting??!!...so why not write 3 as (5-2)... 2 p + 3 p 2^p+3^p = 2 p + ( 5 2 ) p 2^p+(5-2)^p is congruent to 5 p 2 ( p 1 ) 5*p*2^ (p-1) mod 25(This I expect u can show)...So 5 must divide p(WHY?)....Thus p=5 and q n q^n =275...which has got ZERO SOLUTION :) ...This is an ITALIAN MATHEMATICAL OLYMPIAD QUESTION....Hope u liked it...:)

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