How do I find the extrema of a polynomial function on a graphing calculator?
On the TI-83/84/85/89 graphing calculators the buttons that you will need to know to find the maximum and minimum of a function are y=, 2nd, calc, and window.
y=: This button allows you to enter a function into the function bank. This is how you tell the calculator which function you are using. Please clear out any other functions that may already be there.
2nd: This button allows you access to the second function of the buttons. You will need to use calc which is written in a different color. The 2nd button allows access to this function.
Calc: This is found on the top row of the calculator. After selecting this function, the calculator will give you a menu of options. You will want to choose either maximum or minimum.
Window: Many times the local extrema are not visible in the standard window (a 10 x 10 frame). You can adjust the window size to see the part you are interested in.
Here are the steps...
1) Enter the function into the y= bank.
2) Select the 2nd button, followed by the calc button.
3) Select either maximum or minimum depending on the question.
4) If the local extrema are not easily visible, adjust the window.
5) The graph appears on the screen, with the words 'Left Bound?' Move the cursor to the left of the extrema, hit enter.
6) The screen will now say 'Right Bound?', move the cursor to the right of the extrema, hit enter.
7) The screen will say 'Guess?', hit enter
8) The screen will now have the extrema written in terms of x and y on the bottom of the screen.
Hope this helped!