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Let A and B be two square matrices of or...

Let A and B be two square matrices of order 3 such that `|A|=3 and |B|=2`, then the value of
`|A^(-1).adj(B^(-1)).adj(2A^(-1))|` is equal to (where adj(M) represents the adjoint matrix of M)

A

72

B

`(64)/(27)`

C

`(8)/(9)`

D

`(16)/(27)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the value of \( |A^{-1} \cdot \text{adj}(B^{-1}) \cdot \text{adj}(2A^{-1})| \). ### Step-by-Step Solution: 1. **Understanding the Determinants**: We know that for any square matrix \( M \) of order \( n \): \[ |\text{adj}(M)| = |M|^{n-1} \] Here, \( n = 3 \) since \( A \) and \( B \) are \( 3 \times 3 \) matrices. 2. **Calculating \( |A^{-1}| \)**: The determinant of the inverse of a matrix is given by: \[ |A^{-1}| = \frac{1}{|A|} \] Given \( |A| = 3 \), we have: \[ |A^{-1}| = \frac{1}{3} \] 3. **Calculating \( |\text{adj}(B^{-1})| \)**: First, we find \( |B^{-1}| \): \[ |B^{-1}| = \frac{1}{|B|} = \frac{1}{2} \] Now, applying the adjoint property: \[ |\text{adj}(B^{-1})| = |B^{-1}|^{3-1} = \left(\frac{1}{2}\right)^{2} = \frac{1}{4} \] 4. **Calculating \( |\text{adj}(2A^{-1})| \)**: First, we find \( |2A^{-1}| \): \[ |2A^{-1}| = 2^3 |A^{-1}| = 8 \cdot \frac{1}{3} = \frac{8}{3} \] Now, applying the adjoint property: \[ |\text{adj}(2A^{-1})| = |2A^{-1}|^{3-1} = \left(\frac{8}{3}\right)^{2} = \frac{64}{9} \] 5. **Combining the Determinants**: Now we can combine these results: \[ |A^{-1} \cdot \text{adj}(B^{-1}) \cdot \text{adj}(2A^{-1})| = |A^{-1}| \cdot |\text{adj}(B^{-1})| \cdot |\text{adj}(2A^{-1})| \] Substituting the values we calculated: \[ = \frac{1}{3} \cdot \frac{1}{4} \cdot \frac{64}{9} \] 6. **Calculating the Final Value**: \[ = \frac{64}{3 \cdot 4 \cdot 9} = \frac{64}{108} = \frac{16}{27} \] ### Final Answer: Thus, the value of \( |A^{-1} \cdot \text{adj}(B^{-1}) \cdot \text{adj}(2A^{-1})| \) is \( \frac{16}{27} \).
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