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JEE Main & Advanced Sample Paper JEE Main Sample Paper-27

  • question_answer
    If \[A=\left[ \begin{matrix}   1 & 2 & x  \\    3 & -1 & 2  \\ \end{matrix} \right]\] and \[B=\left[ \begin{align}   & y \\  & x \\  & 1 \\ \end{align} \right]\] be such that AB\[AB=\left[ \begin{align}   & 6 \\  & 8 \\ \end{align} \right]\] , then

    A)  \[y=2x\]                                  

    B)  \[y=-x\]

    C)  \[y=x\]                                    

    D)  \[y=-2x\]

    Correct Answer: A

    Solution :

    We get \[\left[ \begin{align}   & 3x+y \\  & -x+3y+2 \\ \end{align} \right]\,=\left[ \begin{align}   & 6 \\  & 8 \\ \end{align} \right]\] \[\Rightarrow \,3x+y=-x+3y\] \[\Rightarrow \,\,4x=2y\] \[\Rightarrow \,2x=y\]


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