### Chapter 3 - Expressions

This chapter discusses algebraic expressions. It contains the following sections:
- section 3.1 - In this section we introduce expressions,
define parts of expression, types of expressions and explain the distributive law.
- section 3.2 - We explain the addition and subtraction of expressions.
- section 3.3 - We give the basic properties of exponents. These properties are required
in the following two sections on the multiplication and division of expressions.
- section 3.4 - We explain the multiplication of expressions.
There are three cases, depending on whether the expressions are monomials or multinomials.
- section 3.5 - We explain the division of expressions.
There are three cases, depending on whether the expressions are monomials or multinomials.
- section 3.6 - We present a data structure called a tree which
holds the structure of an expression.
- section 3.7 - This is a reference section that lists in one place all the
simplifications that could possibly be applied to an expression.