The Coordinate Plane

Two number lines that intersect at right angles form a coordinate plane. The horizontal axis is the x-axis and the vertical axis is the y-axis. The axes intersect at the origin and divide the coordinate plane into four sections called quadrants.

An ordered pair of numbers names the location of a point in the plane. These numbers are the coordinates of the point. Point B has coordinates ( − 3 , 4 ) . open negative 3 comma 4 close .

You use the x-coordinate to tell how far to move right (positive) or left (negative) from the origin. You then use the y-coordinate to tell how far to move up (positive) or down (negative) to reach the point (x, y).

Example 1

Graph each point in the coordinate plane. In which quadrant or on which axis would you find each point?

1. Graph point A ( − 2 , 3 ) eh open negative 2 comma 3 close  in the coordinate plane.

   To graph A ( − 2 , 3 ) , eh open negative 2 comma 3 close comma  move 2 units to the left of the origin. Then move 3 units up. Since the x-coordinate is negative and the y-coordinate is positive, point A is in Quadrant II.

2. Graph point B (2, 0) in the coordinate plane.

   To graph B(2, 0), move 2 units to the right of the origin. Since the y-coordinate is 0, point B is on the x-axis.

Exercises

Name the coordinates of each point in the coordinate plane below.

1. S
2. T
3. U
4. V

Graph each ordered pair in the same coordinate plane.

5. ( 0 , − 5 ) open 0 comma negative 5 close
6. ( 4 , − 1 ) open 4 comma negative 1 close
7. ( − 2 , − 2 ) open negative 2 comma negative 2 close
8. ( − 1 1 2 , 4 ) open . negative 1 , and 1 half , comma 4 . close

In which quadrant or on which axis would you find each point?

9. (0, 10)
10. ( 1 1 2 , − 3 ) open . 1 , and 1 half , comma negative 3 . close
11. ( − 5 , 0 ) open negative 5 comma 0 close
12. ( − 9 , − 2 ) open negative 9 comma negative 2 close

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