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G
RAPHING
T
ECHNOLOGY
G
UIDE
: TI-82
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Figure 2.65: Swap rows 2 and 3 Figure 2.66: Add –4 times row 2 to row 3
To multiply row 2 by –4 and add the results to row 3, thereby replacing row 3 with new values, press MATRX ►
ALPHA A (-) 4, MATRX 1 , 2 , 3) ENTER (see Figure 2.66). The format of this command is *row+(scalar,
matrix, row1, row2).
Technology Tip: It is important to remember that your TI-82 does not store a matrix obtained as the result of any
row operations. So when you need to perform several row operations in succession, it is a good idea to store the
result of each one in a temporary place. You may wish to use matrix [E] to hold such intermediate results.
For example, use elementary row operations to solve this system of linear equations:
239
34
25517
xyz
xy
xyz
−+=
−+ =−
−+=
.
First enter this augmented matrix as [A] in your TI-82:
1239
1304
25517
−
−−
−
. Next store this matrix in [E] (press
MATRX 1 STO➧ MATRX 5 ENTER) so you may keep the original in case you need to recall it.
Here are the row operations and their associated keystrokes. At each step, the result is stored in [E] and replaces the
previous matrix [E]. The solution is shown in Figure 2.67.
Row Operation Keystrokes
row+([E], 1, 2) MATRX ► 9 MATRX 5 , 1 , 2 ) STO➧ MATRX 5 ENTER
*row+(-2, [E], 1, 3) MATRX ► ALPHA A (-) 2, MATRX 5 , 1 , 3 ) STO➧ MATRX 5 ENTER
row+([E], 2, 3) MATRX ► 9 MATRX 5, 2, 3 ) STO➧ MATRX 5 ENTER
*row(
1
2
, [E], 3) MATRX ► 0 1 ÷ 2 , MATRX 5, 3 ) STO➧ MATRX 5 ENTER
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