Identifying Points on a Graph
In algebra, being able to identify the coordinates of a point shown on a graph is just as important as being able to plot points. To identify the x-coordinate of a point on a graph, read the number on the x-axis directly above or below the point. To identify the y-coordinate of a point, read the number on the y-axis directly to the left or right of the point. Remember, to write the ordered pair using the correct order \(\left(x,y\right).\)
Example
Name the ordered pair of each point shown:
Solution
Point A is above \(-3\) on the \(x\text{-axis},\) so the \(x\text{-coordinate}\) of the point is \(-3.\) The point is to the left of \(3\) on the \(y\text{-axis},\) so the \(y\text{-coordinate}\) of the point is \(3.\) The coordinates of the point are \(\left(-3,3\right).\)
Point B is below \(-1\) on the \(x\text{-axis},\) so the \(x\text{-coordinate}\) of the point is \(-1.\) The point is to the left of \(-3\) on the \(y\text{-axis},\) so the \(y\text{-coordinate}\) of the point is \(-3.\) The coordinates of the point are \(\left(-1,-3\right).\)
Point C is above \(2\) on the \(x\text{-axis},\) so the \(x\text{-coordinate}\) of the point is \(2.\) The point is to the right of \(4\) on the \(y\text{-axis},\) so the \(y\text{-coordinate}\) of the point is \(4.\) The coordinates of the point are \(\left(2,4\right).\)
Point D is below \(4\) on the \(x-\text{axis},\) so the \(x\text{-coordinate}\) of the point is \(4.\) The point is to the right of \(-4\) on the \(y\text{-axis},\) so the \(y\text{-coordinate}\) of the point is \(-4.\) The coordinates of the point are \(\left(4,-4\right).\)
Example
Name the ordered pair of each point shown:
Solution
| Point A is on the x-axis at \(x=-4\). | The coordinates of point A are \(\left(-4,0\right)\). |
| Point B is on the y-axis at \(y=-2\) | The coordinates of point B are \(\left(0,-2\right)\). |
| Point C is on the x-axis at \(x=3\). | The coordinates of point C are \(\left(3,0\right)\). |
| Point D is on the y-axis at \(y=1\). | The coordinates of point D are \(\left(0,1\right)\). |