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Which of the following statements are correct ?

A. If the product of 2 non-zero square matrices is a zero matrix, then either A is singular or B is singular

B. If A is a non singular matrix , then ∣A−1∣=1∣A∣|A^{-1}| = \dfrac{1}{|A|}

C. If A is an invertible square matrix then adj AT=1adj Aadj\,A^T = \dfrac{1}{adj\,A}

D. If A and B are invertible matrices then (AB)−1=B−1A−1(AB)^{-1} = B^{-1}A^{-1}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

A is correct: if AB=OAB=O with both non-zero, neither can be invertible, so at least one is singular.

B is the standard result ∣A−1∣=1∣A∣|A^{-1}| = \dfrac{1}{|A|}.

C is incorrect; the correct identity is adj(AT)=(adj A)Tadj(A^T) = (adj\,A)^T, and division by a matrix is undefined.

D is the reversal law for inverses, which is correct.

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