A very common task in math class is to plot and name points on a rectangular coordinate plane, more commonly known as a four-quadrant graph. While this is not at all difficult, many students have a hard time with this task, which leads to difficulty in later math topics which depend on this basic skill. Learning how to read the graph simplifies this task.
If the point rests on the y-axis, it has an x-value of zero. If it rests on the x-axis, it has a y-value of zero.
Study the coordinate plane. Note that the plane (flat, 2D surface) is divided into four quadrants by way of two axes, one vertical and one horizontal. The horizontal axis is called the x-axis, and the vertical axis is the y-axis. Each axis has a positive and negative side. For the x-axis, the positive side is to the right of the y-axis and the negative side is to the left. For the y-axis, the positive side is above the x-axis and the negative side is below it.
Look where the two axes cross. This point is the origin; its coordinates are (0, 0). This means that its "address" is 0 on the x-axis, and 0 on the y-axis. Each increment away from the axes is marked by another grid line. The grid lines often indicate a value of 1, for example, the line one increment up from the x-axis has a y-value of 1, the line two increments up has a y-value of 2. For some purposes, however, each increment might have a value of 10, 100 or 1,000.
Whether the value corresponds with the x- or y-axis is determined by the direction of movement. If your point is vertical, either up or down, this represents a y-value. If your point is horizontal, left or right, this represents an x-value.
Determine first how far left or right to go to be in line with the point, then determine how far up or down to go. The format of a coordinate is always (x, y), written like that in parentheses, separated by a comma. The x-coordinate is always listed before the y-coordinate. You can remember that they are in alphabetical order.
Therefore, to plot the point (-2, 5), move two units to the left relative to the x-axis, and five units up relative to the y-axis.
To name a point on a graph, count how many units from the origin (0,0) to the left or right you go for the x-value, then count how many units up or down you go to get the y-value.
- ruler and pencil image by Hao Wang from Fotolia.com