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The sum of a matrix AA and its transpose is [6−1−14]\begin{bmatrix}6 & -1\\ -1 & 4\end{bmatrix}.

Which of the following statements is true?

Solution

✅ Correct Option: 3

Let A=[abcd]A = \begin{bmatrix}a & b\\ c & d\end{bmatrix}. Then A+AT=[2ab+cb+c2d]A+A^T = \begin{bmatrix}2a & b+c\\ b+c & 2d\end{bmatrix}.

Comparing: 2a=6⇒a=32a=6\Rightarrow a=3, 2d=4⇒d=22d=4\Rightarrow d=2, and b+c=−1⇒c=−1−bb+c=-1\Rightarrow c=-1-b with bb free.

So A=[3b−1−b2]A = \begin{bmatrix}3 & b\\ -1-b & 2\end{bmatrix}.

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