I'm taking an algebra course and was told to purchase Dummit and Foote'sAbstract Algebra, but when I showed up for class I found out that we were using Artin'sAlgebra. I have obtained a copy of the homework problems, but one of them asks us to do something with formulas (1.6) and (6.15) from Chapter 2. Could anyone who owns this book tell me what those two formulae are?

Thanks.