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Question
If A = `[(1,0,1),(0,1,2),(0,0,4)]`, then show that |3A| = 27|A|.
Sum
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Solution
A = `[(1,0,1),(0,1,2),(0,0,4)]`
⇒ 3A = `3[(1,0,1),(0,1,2),(0,0,4)]`
3A = `|(3,0,3), (0,3,6), (0,0,12)|`
L.H.S. = |3A|
= `|(3,0,3), (0,3,6), (0,0,12)|`
= `3|(3,6),(0,12)| - 0|(0,6), (0,12)| + 3|(0,3),(0,0)|`
= (3 × 36) × 0 + 3(0)
= 108
R.H.S. = 27|A|
= `27|(1,0,1), (0,1,2), (0,0,4)|`
= `27[1|(1,2),(0,4)| -0|(0,2), (0,4)| +1|(0,1),(0,0)|]`
= 27[1(4) − 0 + 0]
= 108
Hence, |3A| = 27|A|
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