How to Find the Vertex Using the TI-83 Plus

 

Use the same equation that we started with: 

 

1.  Enter the equation in Y1.

 

Make sure that your plots are turned off.

 

 

2.  Press graph and adjust the window if necessary.  You should be able to see the vertex and all intercepts.

 

Zoom-6 or Zoom-0 may help.

 

The window settings for the graph as shown on the right are:

xmin=-7, xmax=7

ymin=-7, ymax = 7

 

 

 

3.  Press 2nd-Trace to get the Calculate menu.

 

Choose number 3 since our vertex for this graph is the minimum point.

 

You will need to define an area of the graph.  Once this area is defined, the calculator will give you the minimum point for that area.

 

 

4.  Use the left or right blue arrow keys to move the flashing cursor to the left of the vertex and press ENTER to mark the left bound.

 

 

5.  Move the flashing cursor to the right of the vertex and press ENTER to mark the right bound. 

 

Notice the arrow marks at the top of the screen showing the area that you defined.

 

 

6.  Press ENTER when asked Guess?

 

The calculator will display the x- and y-coordinates of the vertex.

 

The coordinates are:  (-1, -4)

 

 

If the vertex is the maximum point as shown in the graph of , you only need to change one step.

 

 

 

 

 

 

In the calculate menu, you will choose number 4:  maximum.

 

Work through the process to make sure that you can get the coordinates of (1, -2)