It is best to find extreme values for a function on a given interval by going through the graph screen. We illustrate with y = x(x - 1)(x + 2). Press MENU 3 to access the equation editor. Then enter the function as Y1. Press F5 to select DRAW. Press SHIFT V-Window to adjust the window for a better view.
To find an extreme value, maximum or minimum, for a function on a given interval, press F4 to access the G-SLV menu. Select 2:Max or 3:Min. We illustrate by finding the left turn around point. Press 2 to select 2:Max. The screen then marks the leftmost maximum point and indicates the coordinates.
Obtaining a minimum value is done in a similar way. The only difference is that from the Math menu, one selects 3:Min rather than 2:Max. Press ESC to return to the graph menu, press F4 to access the G-SLV menu, then press 3 to select 3:Min. In this example, the right turn around point is indicated in the screen at the right.