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Match List-I with List-II

List-IList-II
(A) If AA is a non-singular matrix of order nn, then ∣A(adjA)∣\vert A(\text{adj} A)\vert is equal to(I) ∣A∣n−1\vert A\vert ^{n-1}
(B) If AA is a non-singular matrix of order nn, then ∣adj(adjA)∣\vert \text{adj}(\text{adj} A)\vert is equal to(II) ∣A∣n−2A\vert A\vert ^{n-2} A
(C) If AA is a non-singular matrix of order nn, then adj(adjA)\text{adj}(\text{adj} A) is equal to(III) ∣A∣n\vert A\vert ^n
(D) If AA is a non-singular matrix of order nn, then ∣(adjA)∣\vert (\text{adj} A)\vert is equal to(IV) ∣A∣(n−1)2\vert A\vert ^{(n-1)^2}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

Let's match the properties of adjoint matrices using key formulas.


Key formulas to remember:

∣adj A∣=∣A∣n−1|\text{adj } A| = |A|^{n-1} where nn is the order of matrix

A⋅(adj A)=∣A∣⋅IA \cdot (\text{adj } A) = |A| \cdot I where II is identity matrix

adj(adj A)=∣A∣n−2⋅A\text{adj}(\text{adj } A) = |A|^{n-2} \cdot A for non-singular matrices


(A) Find ∣A(adj A)∣|A(\text{adj } A)|

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

Taking determinant of both sides:

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

=∣A∣n⋅∣I∣= |A|^n \cdot |I|

=∣A∣n⋅1= |A|^n \cdot 1

=∣A∣n= |A|^n

Match: (A) → (III)


(B) Find ∣adj(adj A)∣|\text{adj}(\text{adj } A)|

Using the formula: adj(adj A)=∣A∣n−2⋅A\text{adj}(\text{adj } A) = |A|^{n-2} \cdot A

Taking determinant of both sides:

∣adj(adj A)∣=∣∣A∣n−2⋅A∣|\text{adj}(\text{adj } A)| = ||A|^{n-2} \cdot A|

=(∣A∣n−2)n⋅∣A∣= (|A|^{n-2})^n \cdot |A|

=∣A∣n(n−2)⋅∣A∣= |A|^{n(n-2)} \cdot |A|

=∣A∣n2−2n+1= |A|^{n^2-2n+1}

=∣A∣(n−1)2= |A|^{(n-1)^2}

Match: (B) → (IV)


(C) Find adj(adj A)\text{adj}(\text{adj } A)

This is a direct formula:

adj(adj A)=∣A∣n−2⋅A\text{adj}(\text{adj } A) = |A|^{n-2} \cdot A

Match: (C) → (II)


(D) Find ∣adj A∣|\text{adj } A|

This is a direct formula:

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

Match: (D) → (I)


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

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