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If A is a non-singular square matrix of order n, then which of the following are TRUE ?

A. ∣adjA∣=∣A∣n−1|adj A|=|A|^{n-1}

B. ∣adjA∣=∣A∣n−2|adj A|=|A|^{n-2}

C. ∣adj(adjA)∣=∣A∣(n−2)2|adj (adj A)|=|A|^{(n-2)^2}

D. ∣adj(adjA)∣=∣A∣(n−1)2|adj (adj A)|=|A|^{(n-1)^2}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

The standard result is ∣adjA∣=∣A∣n−1|adj A|=|A|^{n-1}, so A holds and B fails.

Applying it twice, ∣adj(adjA)∣=(∣A∣n−1)n−1=∣A∣(n−1)2|adj(adj A)|=\left(|A|^{n-1}\right)^{n-1}=|A|^{(n-1)^2}, so D holds and C fails.

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