JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Types of matrices, Algebra of matrices

  • question_answer
    If \[A=\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right],\]then \[{{A}^{4}}\]= [EAMCET 1994]

    A) \[\left[ \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right]\]

    B) \[\left[ \begin{matrix}    1 & 1  \\    0 & 0  \\ \end{matrix} \right]\]

    C) \[\left[ \begin{matrix}    0 & 0  \\    1 & 1  \\ \end{matrix} \right]\]

    D) \[\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right]\]

    Correct Answer: A

    Solution :

    We have \[A=\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right]\] So \[{{A}^{2}}=\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right]\,\,\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right]=\left[ \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right]={{I}_{2}}\] \ \[{{A}^{4}}={{A}^{2}}.{{A}^{2}}={{I}_{2}}.{{I}_{2}}={{I}_{2}}=\left[ \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right]\].


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