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Question
Choose the correct answer from the given alternatives in the following question:
If A−1 = `- 1/2[(1,-4),(-1,2)]`, then A = ______.
Options
`[(2,4),(-1,1)]`
`[(2,4),(1,-1)]`
`[(2,-4),(1,1)]`
`[(2,4),(1,1)]`
Solution
`[(2,4),(1,1)]`
Explanation:
A−1 = `1/|"A"|` adj. A
A−1 = `- 1/2[(1,-4),(-1,2)]`
∴ `1/|"A"|` adj. A = `- 1/2[(1,-4),(-1,2)]`
∴ adj. A = `- 1/2[(1,-4),(-1,2)]`
A = `[(2,4),(1,1)]`
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