Review: Graphing in the Coordinate Plane

Use With Lesson 1-9

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 .

The first coordinate is the  x -coordinate. ► ( − 3 , 4 ) ◄ The second coordinate is the  y -coordinate. begin box , table with 2 rows and 1 column , row1 column 1 , cap the first coordinate , row2 column 1 , is the , x . minuscoordinate. , end table , end box . u 2 open negative 3 comma 4 close black left pointing pointer . begin box , table with 2 rows and 1 column , row1 column 1 , cap the second coordinate , row2 column 1 , is the , y . minuscoordinate. , end table , end box

Image Long Description

To reach the point (x, y), 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).

Activity

Play against a partner using two number cubes and a coordinate grid. One cube represents positive numbers and the other cube represents negative numbers.

• During each turn, a player rolls both cubes and adds the numbers to find an x-coordinate. Both cubes are rolled a second time, and the numbers are added to find the y-coordinate. The player graphs the resulting ordered pair on the grid.
• The two players take turns, with each player using a different color to graph points. If an ordered pair has already been graphed, the player does not graph a point, and the turn is over.
• Play ends after each player has completed 10 turns. The player with the most points graphed in a quadrant scores 1 for Quadrant I, 2 for Quadrant II, and so on. Points graphed on either axis do not count. If both players graph an equal number of points in a quadrant, both players score 0 for that quadrant.

Exercises

Describe a pair of number cube rolls that would result in a point plotted at the given location.

1. ( − 3 , 4 ) open negative 3 comma 4 close
2. ( 4 , − 3 ) open 4 comma negative 3 close
3. in Quadrant III
4. the origin

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