**Plot ordered pairs**

** **Each of the pairs of numbers (3, 1), (25, 6), and (4, 21) is an example of an **ordered pair; **that is, a pair of numbers written within parentheses in which the order of the numbers is important. We graph an ordered pair using two perpendicular number lines that intersect at their 0 points, as shown in Figure 2. The common 0 point is called the **origin. **The position of any point in this plane is determined by referring to the horizontal number line, the *x***-axis, **and the vertical umber line, the *y***-axis. **The first number in the ordered pair indicates the position relative to the *x*-axis, and the second number indicates the position relative to the *y*-axis. The *x*-axis and the *y*-axis make up a **rectangular **(or **Cartesian, **for Descartes) **coordinate system.**

To locate, or **plot, **the point on the graph that corresponds to the ordered pair (3, 1), we move three units from 0 to the right along the *x*-axis, and then one unit up parallel to the *y*-axis. The point corresponding to the ordered pair (3, 1) is labeled *A *in Figure 3. Additional points are labeled *B*–*E*. The phrase “the point corresponding to the ordered pair (3, 1)” is often abbreviated

as “the point (3, 1).” The numbers in the ordered pairs are called **components **and are the **coordinates **of the corresponding point.