2008-12.md

course	course_year	question_number	tags	title	year
Groups, Rings and Modules	IB	12	IB 2008 Groups, Rings and Modules	4.I.2G	2008

Let $n \geq 2$ be an integer. Show that the polynomial $\left(X^{n}-1\right) /(X-1)$ is irreducible over $\mathbb{Z}$ if and only if $n$ is prime.

[You may use Eisenstein's criterion without proof.]