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Let A,B,C be 3times3 matrices such that ...

Let `A,B,C` be `3times3` matrices such that `A` is symmetric and `B` and `C` are skew-symmetric. Consider the statements
(`S_1`) `A^(13)B^(26)-B^(26)A^(13)` is symmetric
`(S_(2))A^(26)C^(13)-C^(13)A^(26)` is symmetric Then

A

Only `S_(1)` is true

B

Both `S_(1)` and `S_(2)` are false

C

Both `S_(1)` and `S_(2)` are true `

D

Only `S_(2)` is true

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the two statements regarding the matrices \( A \), \( B \), and \( C \). ### Step 1: Analyze Statement \( S_1 \) **Statement \( S_1 \)**: \( A^{13}B^{26} - B^{26}A^{13} \) is symmetric. 1. **Transpose the Expression**: We need to check if the transpose of \( A^{13}B^{26} - B^{26}A^{13} \) is equal to the original expression. \[ (A^{13}B^{26} - B^{26}A^{13})^T = (A^{13}B^{26})^T - (B^{26}A^{13})^T \] 2. **Apply the Transpose Property**: Using the property \( (XY)^T = Y^T X^T \): \[ (A^{13}B^{26})^T = B^{26^T}A^{13^T} \quad \text{and} \quad (B^{26}A^{13})^T = A^{13^T}B^{26^T} \] 3. **Substituting Transpose of Matrices**: Since \( A \) is symmetric, \( A^{13^T} = A^{13} \). For skew-symmetric matrices, \( B^{26^T} = -B^{26} \): \[ (A^{13}B^{26} - B^{26}A^{13})^T = (-B^{26})A^{13} - A^{13}(-B^{26}) = -B^{26}A^{13} + B^{26}A^{13} = 0 \] 4. **Conclusion for \( S_1 \)**: Since the transpose is equal to the negative of the original expression, \( A^{13}B^{26} - B^{26}A^{13} \) is skew-symmetric, not symmetric. Thus, \( S_1 \) is **false**. ### Step 2: Analyze Statement \( S_2 \) **Statement \( S_2 \)**: \( A^{26}C^{13} - C^{13}A^{26} \) is symmetric. 1. **Transpose the Expression**: Similar to \( S_1 \): \[ (A^{26}C^{13} - C^{13}A^{26})^T = (A^{26}C^{13})^T - (C^{13}A^{26})^T \] 2. **Apply the Transpose Property**: \[ (A^{26}C^{13})^T = C^{13^T}A^{26^T} \quad \text{and} \quad (C^{13}A^{26})^T = A^{26^T}C^{13^T} \] 3. **Substituting Transpose of Matrices**: Again, \( A^{26^T} = A^{26} \) and \( C^{13^T} = -C^{13} \): \[ (A^{26}C^{13} - C^{13}A^{26})^T = (-C^{13})A^{26} - A^{26}(-C^{13}) = -C^{13}A^{26} + C^{13}A^{26} = 0 \] 4. **Conclusion for \( S_2 \)**: Since the transpose is equal to the negative of the original expression, \( A^{26}C^{13} - C^{13}A^{26} \) is skew-symmetric, not symmetric. Thus, \( S_2 \) is also **false**. ### Final Conclusion Both statements \( S_1 \) and \( S_2 \) are false.
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