**Introduction**

In this chapter you learn about relations defined by . You will learn how to rewrite an equation given in the form in the form . You will learn to graph by using the point-slope method as well as how to write the equation of a line from the graph by determining the slope and the intercept.

To write the equation of a line, you must know the slope and the intercept of the line. In this chapter you will learn how to calculate the slope of a line from two given points on the line, from a given equation, from a point on the line and the intercept and from the relationship between special lines. In addition, you will learn how to determine the intercept of a line algebraically.

When these basic concepts have been mastered, you will learn how to determine the equation of lines that are parallel and perpendicular to the and axis or to other lines.

Finally, all of the concepts will be applied to problems that use linear functions as a model.

**Lessons**

In this chapter you will do the following lessons:

- The Slope of a Line from a Graph or from Two Points
- The Equation of a Line in Slope-Intercept Form
- Graphing the Linear Functions
- Determining the Equation of a line from the Graph
- Parallel and Perpendicular Lines
- Linear Function as a Model

## Chapter Outline

- 4.1. The Slope of a Line from a Graph or from Two Points
- 4.2. The Equation of a Line in Slope – Intercept Form
- 4.3. Quiz I
- 4.4. Graphing the Linear Functions y = mx + b; y = a; x = a
- 4.5. Determining the Equation of a Line from the Graph
- 4.6. Parallel and Perpendicular Lines
- 4.7. Quiz II
- 4.8. Linear Function as a Model
- 4.9. Chapter Test