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Let A=(aij)A = (a_{ij}) and B=(bij)B = (b_{ij}) are square matrices of same order.

(A) The number of possible matrices of order 2×22 \times 2 with entries −1,0,1-1, 0, 1 is 81.

(B) A+A′A + A' is skew symmetric matrix

(C) A⋅A−1=0A \cdot A^{-1} = 0, ∣A∣≠0|A| \neq 0

(D) A is skew symmetric matrix if aij=−ajia_{ij} = -a_{ji} for all i,ji, j

(E) (AB)′=A′B′(AB)' = A'B'

Choose the correct answer from the options given below :

Solution

✅ Correct Option: 4

(A) 34=813^4 = 81, true.

(B) (A+A′)′=A′+A=A+A′(A+A')' = A' + A = A+A', so symmetric, not skew. False.

(C) A⋅A−1=IA \cdot A^{-1} = I, not 0. False.

(D) Definition of skew symmetric. True.

(E) (AB)′=B′A′(AB)' = B'A', not A′B′A'B'. False.

So (A) and (D) only.

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