How to Find Max and Min on the TI-83 Plus

By C. C. Edwards

You can use the TI-83 Plus graghing calculator to find the maimum and minimum points on a graph, which has many useful applications. For example, the maximum point on the graph of a profit function not only tells you the maximum profit (the y-coordinate), it also tells you how many items (the x-coordinate) the company must manufacture to achieve this profit.

To find the minimum or maximum value of a function, perform the following steps:

  1. Graph the function in a viewing window that contains the minimum and/or maximum values of the function.

  2. Set the Format menu to ExprOn and CoordOn.

  3. Press [2nd][TRACE] to access the Calculate menu.

  4. Press [3] to find the minimum, or press [4] to find the maximum.

  5. If necessary, repeatedly press

    The up arrow.

    until the appropriate function appears at the top of the screen.

  6. Set the Left Bound of the minimum or maximum point.

    To do so, use the

    The left arrow

    and

    The right arrow

    keys to place the cursor on the graph a little to the left of the location of the minimum or maximum point, and then press [ENTER]. A left bound indicator appears at the top of the screen.

  7. Set the Right Bound for the zero.

    To do so, use the

    left key

    and

    right key

    keys to place the cursor on the graph a little to the right of the location of the minimum or maximum point, and then press [ENTER]. A right bound indicator appears at the top of the screen.

  8. Tell the calculator where you guess the min or max is located.

    To do so, use the

    The left arrow on a TI-83

    and

    The right arrow on a TI-83

    keys to place the cursor on the graph as close to the location of the minimum or maximum point as possible, and then press [ENTER]. The coordinates of the minimum or maximum point appears at the bottom of the screen.

    Graphs of a function on the TI-83