You can use your graphing calculator to check your equation.

Follow the steps below...

1. Create a scatter plot of the points from the given graph by entering the x-values into L₁ and the y-values into L₂.



2. Go to the StatPlot menu by pushing 2^nd, then Y=.



3. Choose one of the Plots (1, 2, or 3) by pressing Enter or the number.

   

4. On the Plot Menu, you do the following:
• Turn the Plot ON by putting your cursor on the ON and pressing Enter.
• Choose the Scatter plot Type of graph by putting your cursor on the first icon on that menu and pressing Enter
• Make sure the Xlist is L₁ and the Ylist is L₂. If either or both need to be changed, just put your cursor on the one you want to change and press 2^nd, then the number of the list you need (for L₁, press 1, etc.)
• Choose a Mark for your points on your plot. Suggest to choose the large “box” mark since there aren’t many points.
5. Set the viewing Window for your scatter plot by pressing WINDOW (second from the left just underneath the graph screen).
• To set the viewing Window, you need to consider the domain and range of your data (points).
• Set the Xmin slightly less than the lowest x-value of your points and the Xmax slightly greater than the largest x-value of your points. Xscl can be set to 1.
• Set the Ymin slightly less than the lowest y-value of your points and the Ymax slightly greater than the largest y-value of your points. Yscl can also be set to 1.
• Leave Xres = 1
6. Press graph and you should see all the points on your scatter plot.



7. Now go to Y= and enter your equation from above 2x² - 4x - 6 and press GRAPH.



8. Since the graph of the equation goes through each and every point of the scatter plot, you can be assured your equation is the correct one for this graph! Voila!

Note: Find more graphing calculator tutorials and applet site links in the resource section.