If A and B are symmetric matrices of same order, then which of the following are correct? (A) $AB-BA$ is a skew-symmetric matrix. Choose the correct answer from the options given below: |
(A), (C) and (D) only (A), (B) and (C) only (C) and (D) only (A) and (D) only |
(A), (C) and (D) only |
The correct answer is Option (1) → (A), (C) and (D) only ** Given: $A$ and $B$ are symmetric matrices. So, $A^{T} = A$ and $B^{T} = B$. (A) $AB - BA$ is skew-symmetric Check transpose: $(AB - BA)^{T} = B^{T}A^{T} - A^{T}B^{T} = BA - AB = -(AB - BA)$ Yes, skew-symmetric. (B) $AB + BA$ is skew-symmetric $(AB + BA)^{T} = BA + AB = AB + BA$ It equals itself → symmetric, not skew. (C) $AB^{T} - BA^{T}$ is skew-symmetric Since $A$ and $B$ are symmetric: $A^{T}=A$, $B^{T}=B$. Expression becomes: $AB - BA$ (same as part A) Skew-symmetric → TRUE. (D) $AB + BA$ is symmetric From part (B), it is symmetric → TRUE. Correct statements: (A), (C), (D). |