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Graphing Technology Guide: TI-92
Since the determinant of the matrix is not zero, it has an inverse matrix. Press A 2nd x–1 ENTER to calculate the
inverse. The result is shown in Figure 5.82.
 x − 2 y + 3z = 9

Now let’s solve a system of linear equations by matrix inversion. Once again consider 
− x + 3 y = −4 . The
2 x − 5 y + 5 z = 17

 1 − 2 3
coefficient matrix for this system is the matrix  −1 3 0  which was entered as matrix a in the previous
 2 −5 5
 9
example. Now enter the matrix  −4  as b. Since b was used before, when we stored 2a as b, press APPS
 17 
6[Data/Matrix Editor] 2[Open] Î 2[Matrix] Ð Ð Î and use Ð to move the cursor to b, then press ENTER twice
to go to the matrix previously saved as b, which can be edited. Return to the Home screen (‹ HOME) and press A
2nd x–1 × B ENTER to get the answer as shown in Figure 5.83.
Figure 5.83: Solution matrix
The solution is still x = 1, y = –l, and z = 2.
5.7 Sequences
5.7.1 Iteration with the ANS key: The ANS key enables you to perform iteration, the process of evaluating a
n −1
n −1
function repeatedly. As an example, calculate
for n = 27. Then calculate
for n = the answer to the
3
3
previous calculation. Continue to use each answer as n in the next calculation. Here are keystrokes to accomplish
this iteration on the TI-92 calculator. (See the results in Figure 5.84.) Notice that when you use ANS in place of n in
a formula, it is sufficient to press ENTER to continue an iteration.
Iteration
1
2
3
4
Keystrokes
27 ENTER
(2nd ANS – 1) ÷ 3 ENTER
ENTER
ENTER
Display
27
8.666666667
2.555555556
.5185185185
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