Question Details

For any two matrices A and B, we have

Options

A

AB = BA

B

AB ≠ BA

C

AB = 0

D

None of these

Correct Answer :

None of these

Solution :

The correct option is None of these.

Let us analyze the behavior of matrix multiplication for any two arbitrary matrices A and B to understand why the other options do not hold generally:
1. Dimension Compatibility: For the product AB to be defined, the number of columns in matrix A must equal the number of rows in matrix B. If A is a matrix of size m×n and B is of size n×p, then the product AB is defined and has size m×p. However, the product BA is only defined if p=m. If pm, then BA does not even exist. Thus, we cannot claim that AB=BA or ABBA universally for any two matrices, as one or both products might be undefined.
2. Non-commutativity: Even when both A and B are square matrices of the same size (so that both AB and BA are defined), matrix multiplication is generally non-commutative. That is, ABBA in most cases. However, there are specific pairs of matrices that do commute (for example, when one of the matrices is the identity matrix I, we have AI=IA=A). Therefore, neither the statement "AB = BA" nor "AB ≠ BA" is universally true for all pairs of matrices.
3. Zero Product: The statement AB=0 (the zero matrix) is only true for specific matrices (such as when one of them is a zero matrix, or when they are zero divisors of each other). It is not a general property for any two matrices.

Since none of the statements "AB = BA", "AB ≠ BA", or "AB = 0" hold universally for any two arbitrary matrices A and B, the correct choice is indeed None of these.

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