1. The problem statement, all variables and given/known data If a>1 is a product of distinct primes, show that xn-a is irreducible over Q for all n ≥ 2. 2. Relevant equations 3. The attempt at a solution I am not really sure how to start this problem. Can anyone point me in the right direction? I know tests for irreducibility for example Eisensteins Criterion or reduction modulo p but I don't think that these are helpful here? Thanks for any help.