Use number lines
A good way to get a picture of a set
of numbers is by using a number line. To construct a number line, choose
any point on a horizontal line and label it 0. Next, choose a point to the right
of 0 and label it 1. The distance from 0 to 1 establishes a scale that can be
used to locate more points, with positive numbers to the right of 0 and negative
numbers to the left of 0. The number 0 is neither positive nor negative.
A number line is shown in Figure 1.
The set of numbers identified on the number line in Figure 1, including
positive and negative numbers and 0, is part of the set of integers, written
I 5 {. . . , 23, 22, 21, 0, 1, 2, 3, . . . }.
Each number on a number line is called the coordinate of the point that
it labels, while the point is the graph of the number. Figure 2 shows a number
line with several selected points graphed on it.
