**Unit 12 Exercises**

**1. **Let *A* be a set. Show that
x *A* = *A* x
= .

**2.** How many different elements does *A* x *B*
have if *A* has *m* elements and *B* has *n* elements?

**3. **Let *A* = {1, 2, 3, 4} and *b* = {0, 3, 5}.
Find

*A**B**A**B**A - B**B - A*

**4. **What can you say about the sets *A* and *B*
if the following are true?

* *a)* A *
*B = A*

* *b) *A - B = A*

**5. **Let *A* and *B* be subsets of a universal set
*U*. Show that *A *
*B*
if and only if
.