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Match List-I with List-II

Let AA be any invertible square matrix. Then

List-IList-II
(A) A−ATA - A^T(I) ∣A∣A−1\vert A\vert A^{-1}
(B) AATA A^T(II) Skew-symmetric
(C) det⁡(A−1)\det (A^{-1})(III) Symmetric
(D) adjA\text{adj} A(IV) [det⁡(A)]−1[\det(A)]^{-1}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

(A−AT)T=AT−(AT)T(A - A^T)^T = A^T - (A^T)^T

=AT−A= A^T - A

=−(A−AT)= -(A - A^T)

Since the transpose equals the negative of itself, A−ATA - A^T is skew-symmetric.

(A)→(II)(A) \rightarrow \text{(II)}


(AAT)T=(AT)T⋅AT(AA^T)^T = (A^T)^T \cdot A^T

=A⋅AT= A \cdot A^T

=AAT= AA^T

Since the transpose equals itself, AATAA^T is symmetric.

(B)→(III)(B) \rightarrow \text{(III)}


Since A⋅A−1=IA \cdot A^{-1} = I, taking determinant on both sides:

det⁡(A)⋅det⁡(A−1)=det⁡(I)=1\det(A) \cdot \det(A^{-1}) = \det(I) = 1

det⁡(A−1)=1det⁡(A)\det(A^{-1}) = \dfrac{1}{\det(A)}

=[det⁡(A)]−1= [\det(A)]^{-1}

(C)→(IV)(C) \rightarrow \text{(IV)}


From the standard identity:

A−1=adj(A)det⁡(A)A^{-1} = \dfrac{\text{adj}(A)}{\det(A)}

adj(A)=det⁡(A)⋅A−1\text{adj}(A) = \det(A) \cdot A^{-1}

=∣A∣ A−1= |A|\,A^{-1}

(D)→(I)(D) \rightarrow \text{(I)}


List-IList-II
(A) A−ATA - A^T(II) Skew-symmetric
(B) AATAA^T(III) Symmetric
(C) det⁡(A−1)\det(A^{-1})(IV) [det⁡(A)]−1[\det(A)]^{-1}
(D) adj(A)\text{adj}(A)(I) ∥A∥A−1\|A\|A^{-1}

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