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If AT=[2312]A^T = \begin{bmatrix} -2 & 3 \\ 1 & 2 \end{bmatrix} and B=[1012]B = \begin{bmatrix} -1 & 0 \\ 1 & 2 \end{bmatrix}, then the matrix (A+2B)T(A + 2B)^T is

Solution

Correct Option: 3

Given AT=[2312]A^T = \begin{bmatrix} -2 & 3 \\ 1 & 2 \end{bmatrix} and B=[1012]B = \begin{bmatrix} -1 & 0 \\ 1 & 2 \end{bmatrix}.

To find (A+2B)T(A + 2B)^T, matrix AA is needed first.

Since ATA^T is given, transpose it to find AA:

A=(AT)TA = (A^T)^T

A=[2312]TA = \begin{bmatrix} -2 & 3 \\ 1 & 2 \end{bmatrix}^T

A=[2132]A = \begin{bmatrix} -2 & 1 \\ 3 & 2 \end{bmatrix}


Calculate 2B2B:

2B=2×[1012]2B = 2 \times \begin{bmatrix} -1 & 0 \\ 1 & 2 \end{bmatrix}

2B=[2024]2B = \begin{bmatrix} -2 & 0 \\ 2 & 4 \end{bmatrix}


Calculate A+2BA + 2B:

A+2B=[2132]+[2024]A + 2B = \begin{bmatrix} -2 & 1 \\ 3 & 2 \end{bmatrix} + \begin{bmatrix} -2 & 0 \\ 2 & 4 \end{bmatrix}

A+2B=[4156]A + 2B = \begin{bmatrix} -4 & 1 \\ 5 & 6 \end{bmatrix}


Calculate (A+2B)T(A + 2B)^T:

(A+2B)T=[4156]T(A + 2B)^T = \begin{bmatrix} -4 & 1 \\ 5 & 6 \end{bmatrix}^T

(A+2B)T=[4516](A + 2B)^T = \begin{bmatrix} -4 & 5 \\ 1 & 6 \end{bmatrix}

Therefore, (A+2B)T=[4516](A + 2B)^T = \begin{bmatrix} -4 & 5 \\ 1 & 6 \end{bmatrix}

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