The Septuagint was a Jewish Bible used by the hellenized Jews for two hundred years before Chirst and at the time when the Apostles wrote the NT, and it contained the books that the Pharisaical bible did not.
It is important because the Apostles quote from the Septuagint and not from the "Hebrew" Bible in over 93% of the cases. You figure out the rest.
I couldn't care less what the Sadducees believed either. I used them to show you that there was no such tinng as one Judaism or that the "Hebrew" Bible was one and the same book you read today in your Old Testament.
ping