CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    For the matrix\[A=\left[ \begin{matrix}    1 & 1 & 0  \\    1 & 2 & 1  \\    2 & 1 & 0  \\ \end{matrix} \right]\]which is correct?

    A)  \[{{A}^{3}}+3{{A}^{2}}-I=0\]

    B)         \[{{A}^{3}}-3{{A}^{2}}-I=0\]

    C)  \[{{A}^{3}}+2{{A}^{2}}-I=0\]

    D)         \[{{A}^{3}}-{{A}^{2}}+I=0\]

    E)  \[{{A}^{3}}+{{A}^{2}}-I=0\]

    Correct Answer: B

    Solution :

    \[\because \]\[A=\left[ \begin{matrix}    1 & 1 & 0  \\    1 & 2 & 1  \\    2 & 1 & 0  \\ \end{matrix} \right]\] \[\therefore \]\[{{A}^{2}}=\left[ \begin{matrix}    2 & 3 & 1  \\    5 & 6 & 2  \\    3 & 4 & 1  \\ \end{matrix} \right]\]and\[{{A}^{3}}=\left[ \begin{matrix}    7 & 9 & 3  \\    15 & 19 & 6  \\    9 & 12 & 4  \\ \end{matrix} \right]\] Hence, \[{{A}^{3}}-3{{A}^{2}}-I=0\]


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