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If A and B are symmetric matrices of same order, then which of the following statements are true?

(A) ABT+BTAAB^T+B^TA is a skew-symmetric matrix.

(B) ABT−BATAB^T-BA^T is a skew-symmetric matrix

(C) (AB)T(AT)−1=B(AB)^T(A^T)^{-1}=B

(D) (AB)−1(BA)T=A(AB)^{-1}(BA)^T=A

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

With AT=AA^T=A and BT=BB^T=B:

(A) AB+BAAB+BA has transpose BA+ABBA+AB, so it is symmetric, not skew.

(B) AB−BAAB-BA has transpose BA−ABBA-AB, its negative, so it is skew-symmetric.

(C) (AB)T(AT)−1=BTAT(AT)−1=BT=B(AB)^T(A^T)^{-1}=B^TA^T(A^T)^{-1}=B^T=B.

(D) (AB)−1(BA)T=B−1A−1AB=I(AB)^{-1}(BA)^T=B^{-1}A^{-1}AB=I, not AA.

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