Re: Every subgroup with indice(index?)2 is normal!Why???

From: Julien Santini (santini.julien_at_wanadoo.fr)
Date: 03/29/05 

Date: Tue, 29 Mar 2005 14:50:00 +0200

> How can I show that every subgroup with indice
>
> (in French, in English perhaps index, but I am not sure,
> it is the cardinalitiy of G(the group) divided by
> the cardinality of the supgroup)
>
> 2 of a finite group is normal!!!
>
> Thank you for answering my question!!!!

Surely someone else will detail your question, but if you can have a look at
the book, try Algebra (Serge Lang) Chap.1 Lemma 6.7. 

--
Julien Santini