Chapter 20

Algebraic Expressions

Algebra allows you to solve problems that are too difficult for arithmetic alone. In algebra, you begin to work with variables (such as x). Each variable in an algebra problem stands in for an unknown number. In this chapter, the focus is on algebraic expressions, which are the building blocks of the algebraic equations that you work with in Chapter 21.

The Problems You’ll Work On

The questions here fall into three general categories:

Evaluation: When you know the value of every variable in an algebraic expression, you can evaluate that expression by plugging in this value. For example, if x = 4, then 3x + 6 = 3(4) + 6 = 18.

Simplification: Even if you don’t know the value of every variable in an algebraic expression, you can often simplify it. For example, 10y – 7y + 2x = 3y + 2x.

Factoring: In some cases, you can factor an algebraic expression by dividing every term by a common factor. For example, when you factor out 3 from the expression 3x – 6, the result is 3(x – 2).

What to Watch Out For

Here is some additional terminology that you may find helpful:

An equation is a mathematical statement with an equal sign, such as 2 + 2 = 4. An algebraic ...