CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    If\[A=\left| \begin{matrix}    3 & 3 & 3  \\    3 & 3 & 3  \\    3 & 3 & 3  \\ \end{matrix} \right|,\]then\[{{A}^{4}}\]is equal to

    A)  27 A                     

    B)         81 A

    C)  243 A   

    D)         729 A

    E)  3 A

    Correct Answer: D

    Solution :

    Given,    \[A=\left[ \begin{matrix}    3 & 3 & 3  \\    3 & 3 & 3  \\    3 & 3 & 3  \\ \end{matrix} \right]\] \[\therefore \]  \[A=3\left| \begin{matrix}    1 & 1 & 1  \\    1 & 1 & 1  \\    1 & 1 & 1  \\ \end{matrix} \right|\] \[\therefore \]  \[{{A}^{2}}=3\left[ \begin{matrix}    1 & 1 & 1  \\    1 & 1 & 1  \\    1 & 1 & 1  \\ \end{matrix} \right].3\left[ \begin{matrix}    1 & 1 & 1  \\    1 & 1 & 1  \\    1 & 1 & 1  \\ \end{matrix} \right]\]                 \[=9\left[ \begin{matrix}    3 & 3 & 3  \\    3 & 3 & 3  \\    3 & 3 & 3  \\ \end{matrix} \right]=9A\] \[\therefore \]  \[{{A}^{4}}={{A}^{2}}.{{A}^{2}}\]                 \[=9A.9A=81{{A}^{2}}=81.9A\]                 \[=729A\]


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