Sefer Shemos opens up with listing Yaakov's sons' names, the fact that they all died, and the fact that the Jews multiplied so rapidly.
My question is: We know most of this already. Why is it repeated? Their names are mentioned several times throughout Parshios Vayeitzei through Vayechi. The fact that at least Yosef died is the last passuk of Bereishis, but we wouldn't know that all of the brothers died before the slavery started without that passuk (see Rashi to Shemos 6:16). And we know that the Jews multiplied rapidly from Bereishis 47:27. So why doesn't Shemos open up with "After Yosef, his brothers, and that entire generation died, a new king arose..."?
EDIT: Apparently there is a debate about whether there are unnecessary words. I guess this question only applies to those who hold there are not.