Match List-I with List-II
Let A be any invertible square matrix. Then
| List-I | List-II | ||
|---|---|---|---|
| (A) | \(A - A^T\) | (I) | \(|A|A^{-1}\) |
| (B) | \(AA^T\) | (II) | Skew-symmetric |
| (C) | \(\det (A^{-1})\) | (III) | Symmetric |
| (D) | \(\mathrm{adj}A\) | (IV) | \([\det(A)]^{-1}\) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
(A) \(A - A^T\)
This matches (II) Skew-symmetric:
\((A - A^T)^T = A^T - A = -(A - A^T)\)
(B) \(AA^T\)
This matches (III) Symmetric, by the reversal law for transposes:
\((AA^T)^T = (A^T)^T A^T = AA^T\)
(C) \(\det (A^{-1})\)
This matches (IV) \([\det(A)]^{-1}\). Since \(AA^{-1} = I\):
\(\det(A)\,\det(A^{-1}) = \det(I) = 1\)
\( \displaystyle \det(A^{-1}) = \frac{1}{\det(A)} = [\det(A)]^{-1} \)
(D) \(\mathrm{adj}A\)
This matches (I) \(|A|A^{-1}\). From \(A\,(\mathrm{adj}A) = |A|\,I\), multiplying on the left by \(A^{-1}\):
\(\mathrm{adj}A = |A|\,A^{-1}\)
So the matching is (A)-(II), (B)-(III), (C)-(IV), (D)-(I).