Page 160 - Numerical Analysis Using MATLAB and Excel

Chapter 4 Matrices and Determinants

7.

13 4 13
31 2 31
–
detA =
23 5 23
)
)
= 1 × 1 × 5 + 3 × – ( 2 × 2 + 4 × 3 × 3 [ – 2 × 1 × 4 + 3 × – ( 2 × 1 + 5 × 3 × 3 ]
–
= 512 + 36 8 + 6 – 45 = – 18
–
11 – 3 – 10
adjA = – 19 – 3 14
7 3 – 8

⁄
⁄
⁄
11 – 3 – 10 – 11 18 318 10 18
– 1 1 1
A = ------------ adjA⋅ = --------- ⋅ – 19 – 3 14 = 19 18 318 – 14 18
⁄
⁄
⁄
detA – 18
⁄
⁄
⁄
7 3 – 8 – 718 – 3 18 818
x
1 – 11 18 318 10 18 – 3 33 18 – 6 18 + 0 27 18 1.50
⁄
⁄
⁄
⁄
⁄
⁄
X = x = 19 18 318 – 14 18 – 2 = – 57 18 – 6 18 + 0 = – 63 18 = – 3.50
⁄
⁄
⁄
⁄
⁄
⁄
2
⁄
⁄
⁄
⁄
⁄
⁄
x – 718 – 3 18 818 0 21 18 + 6 18 + 0 27 18 1.50
3

4−42 Numerical Analysis Using MATLAB® and Excel®, Third Edition

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