**Unit 13 Exercises**

**1. **Let *A *and *B *be sets.
Show that

*A**B = B**A.**A**B = B**A*.

**2. **Show that if *A* and *B* are sets,
then
*=*

by showing each side is a subset of the other side.

**3. **Let *A*, *B*, and *C* be sets.
Show that *A *
( *B *
*C* ) =
( *A *
*B * )
*C.*

* *