COORDINATE GRAPHS

LOCATING POINTS

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 Locating Points

Step 1 | Start at the origin, coordinates ( 0 , 0 ).
Step 2 | If the x-coordinate in the ordered pair is a positive number, move right along the x-axis the same number of units as the x-coordinate. If the x-coordinate in the ordered pair is a negative number, move left along the x-axis the same number of units as the x-coordinate.
Step 3 | Mark your location on the x-axis.
Step 4 | From this point on the x-axis, if the y-coordinate in the ordered pair is a positive number, move up the same number of units as the y-coordinate. If the y-coordinate in the ordered pair is a negative number, move down from this point the same number of units as the y-coordinate..
Step 5 | Mark your location. You have now located the point indicated by the ordered pair.

Example Locate the point ( -2 , 9 )

Step 1 | Start at the origin, coordinates ( 0 , 0 ). | ( 0 , 0 )
Step 2 | If the x-coordinate in the ordered pair is a positive number, move right along the x-axis the same number of units as the x-coordinate. If the x-coordinate in the ordered pair is a negative number, move left along the x-axis the same number of units as the x-coordinate. | Move left 2 units starting at (0,0)
Step 3 | Mark your location on the x-axis. | Mark your location on the x-axis (-2)
Step 4 | From this point on the x-axis, if the y-coordinate in the ordered pair is a positive number, move up the same number of units as the y-coordinate. If the y-coordinate in the ordered pair is a negative number, move down from this point the same number of units as the y-coordinate.. | Move up 9 units
Step 5 | Mark your location. You have now located the point indicated by the ordered pair. | point located at ( -2 , 9 )