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If A and B are non- singular square matr...

If A and B are non- singular square matrix of same order `3xx3`, then which of the following options is correct?

A

`|adj(AB)|=|A||B|`

B

`|(adjAB)^(-1)|=|adj(AB)|`

C

`|adj(AB)^(-1)|=|adj(AB)^(-1)|`

D

`|adj(AB)^(T)|=|AB|^(-2)`

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the properties of non-singular square matrices and their determinants, particularly focusing on the adjoint and inverse operations. ### Step-by-Step Solution: 1. **Understanding Non-Singular Matrices**: - A non-singular matrix is one that has an inverse. For a matrix \( A \) of order \( n \), if \( \text{det}(A) \neq 0 \), then \( A \) is non-singular. 2. **Properties of Determinants**: - For any two \( n \times n \) matrices \( A \) and \( B \): \[ \text{det}(AB) = \text{det}(A) \cdot \text{det}(B) \] - The determinant of the adjoint of a matrix \( A \) is given by: \[ \text{det}(\text{adj}(A)) = (\text{det}(A))^{n-1} \] - For a \( 3 \times 3 \) matrix, this becomes: \[ \text{det}(\text{adj}(A)) = (\text{det}(A))^2 \] 3. **Analyzing the Options**: - **Option A**: \( \text{adj}(AB) = \text{det}(A) \cdot \text{det}(B) \) - This is incorrect because \( \text{adj}(AB) = \text{adj}(A) \cdot \text{adj}(B) \) and not equal to the product of the determinants. - **Option B**: \( \text{det}(\text{adj}(AB^{-1})) = \text{adj}(A) \cdot \text{adj}(B) \) - This is also incorrect. The correct relation involves the determinant of the adjoint and the determinant of the inverse, which leads to a different expression. - **Option C**: \( \text{adj}(AB^{-1}) = \text{adj}(A) \cdot \text{adj}(B^{-1}) \) - This is correct. The adjoint of the product of matrices is the product of their adjoints in reverse order. 4. **Conclusion**: - After evaluating the options, we find that the correct statement is: \[ \text{adj}(AB^{-1}) = \text{adj}(A) \cdot \text{adj}(B^{-1}) \] - Therefore, the correct answer is **Option C**.
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