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Question
If A = `[(1,1,-2),(2,1,-3),(5,4,-9)]`, find |A|.
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Solution
A = `[(1,1,-2),(2,1,-3),(5,4,-9)]`
|A| = `|(1,1,-2),(2,1,-3),(5,4,-9)|`
= `1|(1,-3), (4,-9)| -1 |(2,-3),(5,-9)| + (-2)|(2,1),(5,4)|`
= 1(−9 + 12) − 1(−18 + 15) + (−2)(8 − 5)
= 1(3) − 1(−3) + (−2)(3)
= 3 + 3 − 6
= 0
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