Finding the maximum or minimum point on a graph on your TI-84 Plus calculator has many useful applications. For example, the maximum point on the graph of a profit function tells you not only the maximum profit (the y-coordinate), but also 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:
Graph the function in a viewing window that contains the minimum and/or maximum values of the function.
Press [2nd][TRACE] to access the Calculate menu.
Press [3] to find the minimum, or press [4] to find the maximum.
If necessary, repeatedly press the up- and down-arrow keys until the appropriate function appears in the border at the top of the screen.
Set the Left Bound of the minimum or maximum point.
To do so, use the left- and 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 (the dotted line with a triangular indicator shown in the first screen) appears on the screen.
Set the Right Bound for the zero.
To do so, use the left- and right-arrow 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 (the rightmost dotted line with the triangular indicator in the second screen) appears on the screen.
Tell the calculator where you guess the min or max is located.
To do so, use the left- and right-arrow 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 in the border at the bottom of the screen (as shown in the third screen).