Exercise 22 Page 602

In an ( x, y) ordered pair, the first number tells us the x-coordinate of the point and the second number tells us the y-coordinate of the point. To graph A( 3, 7), we first find 3 on the x-axis and make a mental note of this grid line. The x-coordinate 3 tells us to move 3 units to the right of the origin — the positive horizontal direction.

Next, we find 7 on the y-axis and follow this grid line until it collides with the grid line from our x-coordinate. The y-coordinate 7 tells us to move 7 units up from the origin — the positive vertical direction.

The point A( 3, 7) lies on the point at which these two grid lines intersect.

Extra

Quadrants of the Coordinate Plane

One common way that mathematicians describe points on a coordinate plane is by naming the quadrant in which the point lies. There are four quadrants and they are divided by the x- and y-axes.

The four quadrants are named using numbers. For example, the quadrant containing the positive x- and y-coordinates is either called Quadrant (I), the first quadrant, or Q1.