Texas Instruments TI-92 Getting Started page 18

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Graphing Technology Guide: TI-92

Now move to a point right of the minimum/maximum and set a upper bound by pressing ENTER. The coordinates

of the relative minimum/maximum point will be displayed (see Figure 5.52). Good choices for the left bound and

right bound can help the TI-92 work more efficiently and quickly.

Figure 5.52: Relative minimum on y = –x

+ 4x

Note that if you have more than one graph on the screen, the upper right corner of the TI-83 screen will show the

number of the function whose minimum/maximum is being calculated.

5.3 Solving Equations and Inequalities

5.3.1 Intercepts and Intersections: Tracing and zooming are also used to locate an x-intercept of a graph, where a

curve crosses the x-axis. For example, the graph of y = x

– 8x crosses the x-axis three times (Figure 5.53). After

tracing over to the x-intercept point that is farthest to the left, zoom in (Figure 5.54). Continue this process until you

have located all three intercepts with as much accuracy as you need. The three x-intercepts of y = x

– 8x are

approximately –2.828, 0, and 2.828.

Figure 5.53: Graph of y = x

– 8x

Figure 5.54: Near an x-intercept of y = x

– 8x

Technology Tip: As you zoom in, you may also wish to change the spacing between tick marks on the x-axis so that

the viewing rectangle shows scale marks near the intercept point. Then the accuracy of your approximation will be

such that the error is less than the distance between two tick marks. Change the x-scale on the TI-92 from the

WINDOW menu. Move the cursor down to xscl and enter an appropriate value.

The x-intercept of a function's graph is a zero of the function, so while viewing the graph, press F5[Math] (Figure

5.50) and choose 2[Zero] to find a zero of this function. Set a lower bound and upper bound as described in Section

5.2.7. The TI-92 shows the coordinates of the point and indicates that it is a zero (Figure 5.55)