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If [121][−10112−1013][2xx−7]=[0][1 \quad 2 \quad 1] \begin{bmatrix} -1 & 0 & 1 \\ 1 & 2 & -1 \\ 0 & 1 & 3 \end{bmatrix} \begin{bmatrix} 2x \\ x \\ -7 \end{bmatrix} = [0], then the value of xx is

Solution

✅ Correct Option: 2

Multiply the first two matrices: [1  2  1][1\;2\;1] times the 3×33\times3 matrix gives [1  5  2][1\;5\;2]. Then [1  5  2][2xx−7]=2x+5x−14=7x−14[1\;5\;2]\begin{bmatrix}2x\\x\\-7\end{bmatrix}=2x+5x-14=7x-14. Setting this to 0 gives x=2x=2.

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