JEE Main & Advanced JEE Main Solved Paper-2017

  • question_answer
    If \[A\left[ \begin{matrix}    2 & -3  \\    -4 & 1  \\ \end{matrix} \right],\]then adj \[(3{{A}^{2}}+12A)\]is equal to:-                                                  JEE Main Solved Paper-2017

    A)  \[\left[ \begin{matrix}    72 & -63  \\    -84 & 51  \\ \end{matrix} \right]\]   

    B)  \[\left[ \begin{matrix}    72 & -84  \\    -63 & 51  \\ \end{matrix} \right]\]

    C)  \[\left[ \begin{matrix}    51 & 63  \\    84 & 72  \\ \end{matrix} \right]\]                   

    D)  \[\left[ \begin{matrix}    51 & 84  \\    63 & 72  \\ \end{matrix} \right]\]

    Correct Answer: C

    Solution :

     Given \[A=\left[ \begin{matrix}    2 & -3  \\    -4 & 1  \\ \end{matrix} \right]\]                 \[3{{A}^{2}}=\left[ \begin{matrix}    16 & -9  \\    -12 & 13  \\ \end{matrix} \right]\]                 \[12A=\left[ \begin{matrix}    24 & -36  \\    -48 & 12  \\ \end{matrix} \right]\]                 \[\therefore \]  \[3{{A}^{2}}+12A=\left[ \begin{matrix}    72 & -63  \\    -84 & 51  \\ \end{matrix} \right]\]                 adj\[(3{{A}^{2}}+12A)=\left[ \begin{matrix}    51 & 63  \\    84 & 72  \\ \end{matrix} \right]\]


You need to login to perform this action.
You will be redirected in 3 sec spinner