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Let AA be a non-singular square matrix of order nn, then

Match List-I with List-II

List-IList-II
(A) A(adjA)A(\text{adj} A)(I) 1∣A∣\frac{1}{\vert A\vert }
(B) ∣adjA∣\vert \text{adj} A\vert (II) ∣A∣n\vert A\vert ^n
(C) ∣A−1∣\vert A^{-1}\vert (III) ∣A∣I\vert A\vert I
(D) ∣A(adjA)∣\vert A(\text{adj} A)\vert (IV) ∣A∣n−1\vert A\vert ^{n-1}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

For a non-singular square matrix AA of order nn, the following standard results hold:

A(adj A)=∣A∣⋅IA(\text{adj } A) = |A| \cdot I

∣adj A∣=∣A∣n−1|\text{adj } A| = |A|^{n-1}

∣A−1∣=1∣A∣|A^{-1}| = \dfrac{1}{|A|}

∣kI∣=kn|kI| = k^n for an n×nn \times n matrix


(A) A(adj A)A(\text{adj } A)

A(adj A)=∣A∣⋅IA(\text{adj } A) = |A| \cdot I

Matches with (III)


(B) ∣adj A∣|\text{adj } A|

∣adj A∣=∣A∣n−1|\text{adj } A| = |A|^{n-1}

Matches with (IV)


(C) ∣A−1∣|A^{-1}|

Since ∣A∣⋅∣A−1∣=∣AA−1∣=∣I∣=1|A| \cdot |A^{-1}| = |AA^{-1}| = |I| = 1

∣A−1∣=1∣A∣|A^{-1}| = \dfrac{1}{|A|}

Matches with (I)


(D) ∣A(adj A)∣|A(\text{adj } A)|

From (A), A(adj A)=∣A∣⋅IA(\text{adj } A) = |A| \cdot I

Taking determinant on both sides:

∣A(adj A)∣=∣∣A∣⋅I∣|A(\text{adj } A)| = \big||A| \cdot I\big|

=∣A∣n⋅∣I∣= |A|^n \cdot |I|

=∣A∣n= |A|^n

Matches with (II)


(A) → (III), (B) → (IV), (C) → (I), (D) → (II)

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