COORDINATE GRAPHS

GETTING THE COORDINATES

Concept: A coordinate graph is a system for finding the location of a point, or several points, on a flat surface called a plane. A coordinate graph is formed from two axis lines that cross at a point called the origin. The horizontal line is the x-axis and the vertical line is the y-axis. Both lines are marked as number lines with the origin at zero. The axes divide the graph into four quadrants, labeled I, II, III, and IV.

Each point on the grid is named by two numbers, an x-coordinate and a y-coordinate. The x-coordinate is always written first; the y-coordinate is always written second. Together the coordinates are called an ordered pair and are enclosed in parentheses, separated by a comma like this: (x, y) .

Steps for Getting the Coordinates

Step 1 | Start at the origin, coordinates ( 0 , 0 ).
Step 2 | Move left or right along the x-axis, until directly above or below the selected point on the grid.
Step 3 | Count the number of units you moved, and mark that number in the first position of the ordered pair. If you moved to the right, your number will be a positive number. If you moved to the left, your number will be a negative number.
Step 4 | Move up or down the y-axis until you are directly across from the selected point on the grid.
Step 5 | Mark the number of units you moved in the second position of the ordered pair. If you moved up, your number will be a positive number. If you moved down, your number will be a negative number.
| By naming both the x and y coordinates, you have created an ordered pair for a selected point on the grid.

Example Find the x-y coordinate (ordered pair) of the point (marked in red) on the grid.

tep 1 | Start at the origin, coordinates ( 0 , 0 ). | ( 0 , 0 )
Step 2 | Move left or right along the x-axis, until directly above or below the selected point on the grid. | Move right from (0,0)
Step 3 | Count the number of units you moved, and mark that number in the first position of the ordered pair. If you moved to the right, your number will be a positive number. If you moved to the left, your number will be a negative number. | 9 units to the right, starting at (0,0) x-coordinate is ( 9 , )
Step 4 | Move up or down the y-axis until you are directly across from the selected point on the grid. | Move down, away from x-axis
Step 5 | Mark the number of units you moved in the second position of the ordered pair. If you moved up, your number will be a positive number. If you moved down, your number will be a negative number. | 7 units Down x-coordinate is ( 9 , -7 )
| By naming both the x and y coordinates, you have created an ordered pair for a selected point on the grid. | ( 9 , -7 )