Notice that if you move the same number of units to the left or right of the vertex, the y-coordinates are the same. For example, one x-unit to the left and to the right of (-1, -9) have the same y-coordinates, (-2, -8) and (0, -8).

If you move two x-units to the left or right of the vertex of (-1, 9), the y-coordinates are also the same, (-3, -5) and (1, -5).

Therefore, once you identify the vertex of a parabola, you can use symmetry to find points for your table.

• The vertex lies on the axis of symmetry, its y-coordinate only shows up once and is either the minimum or maximum value of the function.

Another Example

Use the graph shown below to create a table of values.

Click here for extra practice.