- Thread starter
- Moderator
- #1

- Jan 26, 2012

- 995

-----

**Problem**: Let $H$ and $K$ be subgroups of a group $G$. Define $HK = \{hk : h\in H, k\in K\}$. Show that $HK$ is a subgroup of $G$ if and only if $HK=KH$.

-----

Remember to read the POTW submission guidelines to find out how to submit your answers!