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If A=[100−1]A = \begin{bmatrix} 1 & 0 \\ 0 & -1 \end{bmatrix} and B=[0110]B = \begin{bmatrix} 0 & 1 \\ 1 & 0 \end{bmatrix} then the matrix AB is equal to

Solution

✅ Correct Option: 3

Given matrices:

A=[100−1]A = \begin{bmatrix} 1 & 0 \\ 0 & -1 \end{bmatrix}

B=[0110]B = \begin{bmatrix} 0 & 1 \\ 1 & 0 \end{bmatrix}


For matrix multiplication ABAB, each entry is computed as (row of A) × (column of B).

Top-left entry (row 1 of A × column 1 of B):

(1)(0)+(0)(1)(1)(0) + (0)(1)

=0= 0


Top-right entry (row 1 of A × column 2 of B):

(1)(1)+(0)(0)(1)(1) + (0)(0)

=1= 1


Bottom-left entry (row 2 of A × column 1 of B):

(0)(0)+(−1)(1)(0)(0) + (-1)(1)

=−1= -1


Bottom-right entry (row 2 of A × column 2 of B):

(0)(1)+(−1)(0)(0)(1) + (-1)(0)

=0= 0


Therefore:

AB=[01−10]AB = \begin{bmatrix} 0 & 1 \\ -1 & 0 \end{bmatrix}

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