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Identify the correct statements.

(A) If AA is a non-singular matrix, then A−1=∣A∣(adj A)A^{-1} = \frac{|A|}{(\text{adj } A)}

(B) If AA is an invertible matrix then 1∣A−1∣=∣A∣\frac{1}{|A^{-1}|} = |A|

(C) If AA and BB are two invertible matrices of the same order then ABAB is also invertible matrix and (BA)−1=A−1B−1(BA)^{-1} = A^{-1}B^{-1}

(D) If AA is an invertible matrix, then ATA^T is also invertible and (AT)−1=1(A−1)T(A^T)^{-1} = \frac{1}{(A^{-1})^T}

Choose the correct answer from the options given below :

Solution

✅ Correct Option: 1

(A) is wrong; the correct formula is A−1=adj A∣A∣A^{-1} = \frac{\text{adj }A}{|A|}. (B) is correct since ∣A−1∣=1/∣A∣|A^{-1}| = 1/|A|. (C) is correct: (BA)(A−1B−1)=B(AA−1)B−1=I(BA)(A^{-1}B^{-1}) = B(AA^{-1})B^{-1} = I, so (BA)−1=A−1B−1(BA)^{-1} = A^{-1}B^{-1}. (D) has a malformed expression. So (B) and (C) only.

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