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If A is an invertible matrix of order...

If `A` is an invertible matrix of order `3xx3` such that `|A|=2` . Then, find `a d j\ (a d j\ A)` .

A

`abs(A)A`

B

`abs(A)^2A`

C

`abs(A)^(-1)A`

D

none of these

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The correct Answer is:
To solve the problem, we need to find \( \text{adj}(\text{adj}(A)) \) given that \( A \) is an invertible matrix of order \( 3 \times 3 \) and \( |A| = 2 \). ### Step-by-Step Solution: 1. **Understanding the Properties of the Adjoint**: The adjoint of a matrix \( A \), denoted as \( \text{adj}(A) \), has a specific relationship with the determinant of \( A \). For a square matrix \( A \) of order \( n \): \[ A \cdot \text{adj}(A) = |A| I_n \] where \( I_n \) is the identity matrix of order \( n \). 2. **Finding \( \text{adj}(A) \)**: Since \( |A| = 2 \) and \( n = 3 \), we can express: \[ A \cdot \text{adj}(A) = 2 I_3 \] 3. **Finding \( \text{adj}(\text{adj}(A)) \)**: There is a property that states: \[ \text{adj}(\text{adj}(A)) = |A|^{n-1} A \] For our matrix \( A \) of order \( 3 \): \[ \text{adj}(\text{adj}(A)) = |A|^{3-1} A = |A|^2 A \] 4. **Substituting the Determinant**: We know \( |A| = 2 \): \[ \text{adj}(\text{adj}(A)) = 2^2 A = 4A \] ### Final Answer: Thus, the result is: \[ \text{adj}(\text{adj}(A)) = 4A \]

To solve the problem, we need to find \( \text{adj}(\text{adj}(A)) \) given that \( A \) is an invertible matrix of order \( 3 \times 3 \) and \( |A| = 2 \). ### Step-by-Step Solution: 1. **Understanding the Properties of the Adjoint**: The adjoint of a matrix \( A \), denoted as \( \text{adj}(A) \), has a specific relationship with the determinant of \( A \). For a square matrix \( A \) of order \( n \): \[ A \cdot \text{adj}(A) = |A| I_n ...
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OBJECTIVE RD SHARMA ENGLISH-MATRICES-Section I - Solved Mcqs
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