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Let AA and BB be two non-singular, square matrices of same order, and

A. (AB)−1=B−1⋅A−1(AB)^{-1} = B^{-1} \cdot A^{-1}

B. (A+B)−1=B−1+A−1(A+B)^{-1} = B^{-1} + A^{-1}

C. adj.A=∣A∣⋅A−1adj. A = |A| \cdot A^{-1}

D. det(A−1)=[detA]−1det(A^{-1}) = [det A]^{-1}

Choose the correct answer from the options given below

Solution

✅ Correct Option: 4

A is correct: (AB)−1=B−1A−1(AB)^{-1} = B^{-1}A^{-1} is a standard property. B is incorrect: (A+B)−1≠B−1+A−1(A+B)^{-1} \neq B^{-1}+A^{-1} in general. C is correct: adj(A)=∣A∣⋅A−1adj(A) = |A| \cdot A^{-1} follows from A⋅adj(A)=∣A∣IA \cdot adj(A) = |A|I. D is correct: det(A−1)=1/det(A)=(detA)−1det(A^{-1}) = 1/det(A) = (det A)^{-1}. So A, C and D only are correct.

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