Prove that the fraction (21n+4)/(14n+3) is irreducible for every natural number n.

Source: Russian IMO

(3(7n+4/3))/(2(7n+3/2)) = 3/2-1/(2(14n+3)) = 3/2-1/(28n+6)

Doesn't look likely, does it? Are the Russians going soft these days?

 

Edited on March 29, 2013, 10:41 am

Posted by broll on 2013-03-29 10:32:05