Coordinate GraphingCoordinate graphing sounds very dramatic but it is actually just a visual method for showing relationships between numbers. The relationships are shown on a coordinate grid. A coordinate grid has two perpendicular lines, or axes, labeled like number lines. The horizontal axis is called the xaxis. The vertical axis is called the yaxis. The point where the xaxis and yaxis intersect is called the origin.
The numbers on a coordinate grid are used to locate points. Each point can be identified by an ordered pair of numbers; that is, a number on the xaxis called an xcoordinate, and a number on the yaxis called a ycoordinate. Ordered pairs are written in parentheses (xcoordinate, ycoordinate). The origin is located at (0,0). Note that there is no space after the comma. The location of (2,5) is shown on the coordinate grid below. The xcoordinate is 2. The ycoordinate is 5. To locate (2,5), move 2 units to the right on the xaxis and 5 units up on the yaxis.
The order in which you write x and ycoordinates in an ordered pair is very important. The xcoordinate always comes first, followed by the ycoordinate. As you can see in the coordinate grid below, the ordered pairs (3,4) and (4,3) refer to two different points!
The function table below shows the x and ycoordinates for five ordered pairs. You can describe the relationship between the x and ycoordinates for each of these ordered pairs with this rule: the xcoordinate plus two equals the ycoordinate. You can also describe this relationship with the algebraic equation x + 2 = y.
To graph the equation x + 2 = y , each ordered pair is located on a coordinate grid, then the points are connected. Notice that the graph forms a straight line. The arrows indicate that the line goes on in both directions. The graph for any simple addition, subtraction, multiplication, or division equation forms a straight line.

Finding and Graphing Points for Linear Relationships
Finding the Length of a Line 
