Basic Math and Pre-Algebra Workbook For Dummies, 2nd Edition

Chapter 13

Getting Graphic: Xy-Graphs

In This Chapter

Understanding the basics of the xy-graph

Plotting points and drawing lines on the xy-graphs

A graph is a visual tool for providing information about numbers. Graphs commonly appear in business reports, sales brochures, newspapers, and magazines — any place where conveying numerical information quickly and clearly is important.

In this chapter, I show you how to work with the graph that's most commonly used in mathematics: the xy-graph.

Getting the Point of the Xy-Graph

In math, the most commonly used graph is the xy-graph (also called the Cartesian coordinate system or the Cartesian plane). The xy-graph is basically two number lines that cross at 0. These number lines are called the x-axis (which runs horizontally) and the y-axis (which runs vertically). These two axes (plural of axis) cross at a point called the origin.

Every point on the xy-graph is represented by a pair of numbers in parentheses, called a set of xy-coordinates (or an ordered pair). The first number is called the x-coordinate, and the second is called the y-coordinate.

To plot (locate) a point on the xy-graph, start at the origin (0,0) and follow the coordinates: ...