Texas Instruments TI-82 Manual page 17

2.3.4 Solving Inequalities by Graphing: Consider the inequality
3 x
y = −
the two functions 1
2
inequality is true when the graph of
x ≤ , or (–∞, 2].
solution is the half-line 2
The TI-82 is capable of shading the region above or below a graph or between two graphs. For example, to graph y
2
≥ x –1, first graph the function y = x
Figure 2.51). These keystrokes instruct the TI-82 to shade the region above y = x
because this is the greatest y-value in the graph window) with shading resolution value of 2. The result is shown in
Figure 2.52.
To clear the shading, press 2nd DRAW 1.
Figure 2.51: DRAW Shade
17
G T
RAPHING ECHNOLOGY
Figure 2.49: Solving a system of equations
and y = x – 4 (Figure 2.50). First locate their point of intersection, at x = 2. The
3 x
y = −
lies above the graph of y = x – 4, and that occurs when x < 2 . So the
1
2
Figure 2.50: Solving
2
–1 as Y . Then press 2nd DRAW 7 2nd Y-
1
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G : TI-82
UIDE
3 x
− ≥ − . To solve it with your TI-82, graph
1 x 4
2
3 x
− ≥ −
1 x 4
2
1 1 , 10 , 2 ) ENTER (see
VARS
2
–1 and below y = 10 (chosen
Figure 2.52: Graph of y ≥ x
2
–1