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

A. AB is symmetric matrix

B. AB - BA is skew symmetric matrix

C. BTABB^TAB is symmetric matrix

D. A−ATA - A^T is skew symmetric matrix

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

ABAB is symmetric only when AB=BAAB = BA, so A is not always true.

(AB−BA)T=BA−AB=−(AB−BA)(AB-BA)^T = BA-AB = -(AB-BA), so B is skew symmetric.

(BTAB)T=BTATB=BTAB(B^TAB)^T = B^TA^TB = B^TAB, so C is symmetric.

A−ATA-A^T is always skew symmetric (here it is the zero matrix, which is skew symmetric), so D is true.

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