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J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    If \[x\left[ \begin{matrix}    -3  \\    4  \\ \end{matrix} \right]+y\left[ \begin{matrix}    4  \\    3  \\ \end{matrix} \right]=\left[ \begin{matrix}    10  \\    -5  \\ \end{matrix} \right],\] then

    A)  \[x=-2,\,y=1\]

    B)  \[x=-9,y=10\]

    C)  \[x=22,y=1\]

    D)  \[x=2,y=-1\]

    Correct Answer: A

    Solution :

    Given that,  \[x\left[ \begin{matrix}    -3  \\    4  \\ \end{matrix} \right]+y\left[ \begin{matrix}    4  \\    3  \\ \end{matrix} \right]=\left[ \begin{matrix}    10  \\    -5  \\ \end{matrix} \right]\] \[\therefore \] \[-3x+4y=10\] ?.(i) and \[4x+3y=-5\] ?.(ii) On multiplying Eq. (i) by 4 and Eq. (ii) by 4 and then subtracting, we get \[-25x=50\] \[\Rightarrow \] \[x=-2\]


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