BCECE Engineering BCECE Engineering Solved Paper-2007

  • question_answer
    If\[\left| \begin{matrix}    -12 & 0 & \lambda   \\    0 & 2 & -1  \\    2 & 1 & 15  \\ \end{matrix} \right|=-360,\]then the value of \[\lambda \]is

    A)  \[-1\]                   

    B)         \[-2\]                   

    C)         \[-3\]                                   

    D)  \[4\]

    Correct Answer: C

    Solution :

    \[\left| \begin{matrix}    -12 & 0 & \lambda   \\    0 & 2 & -1  \\    2 & 1 & 15  \\ \end{matrix} \right|=-360\] \[\Rightarrow \]               \[-12\left| \begin{matrix}    2 & -1  \\    1 & 15  \\ \end{matrix} \right|+\lambda \left| \begin{matrix}    0 & 2  \\    2 & 1  \\ \end{matrix} \right|=-360\] \[\Rightarrow \]               \[-12(30+1)-4\lambda =-360\] \[\Rightarrow \]               \[-372+360=4\lambda \] \[\Rightarrow \]               \[\lambda =-\frac{12}{4}=-3\]


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