Skip to main contentSkip to solution

Match List-I with List-II

Let AA be any invertible square matrix. Then

List-IList-II
(A) AATA - A^T(I) AA1\vert A\vert A^{-1}
(B) AATA A^T(II) Skew-symmetric
(C) det(A1)\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

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

=ATA= A^T - A

=(AAT)= -(A - A^T)

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

(A)(II)(A) \rightarrow \text{(II)}


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

=AAT= A \cdot A^T

=AAT= AA^T

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

(B)(III)(B) \rightarrow \text{(III)}


Since AA1=IA \cdot A^{-1} = I, taking determinant on both sides:

det(A)det(A1)=det(I)=1\det(A) \cdot \det(A^{-1}) = \det(I) = 1

det(A1)=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:

A1=adj(A)det(A)A^{-1} = \dfrac{\text{adj}(A)}{\det(A)}

adj(A)=det(A)A1\text{adj}(A) = \det(A) \cdot A^{-1}

=AA1= |A|\,A^{-1}

(D)(I)(D) \rightarrow \text{(I)}


List-IList-II
(A) AATA - A^T(II) Skew-symmetric
(B) AATAA^T(III) Symmetric
(C) det(A1)\det(A^{-1})(IV) [det(A)]1[\det(A)]^{-1}
(D) adj(A)\text{adj}(A)(I) AA1\|A\|A^{-1}

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question