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

  • question_answer
    If \[X=\left[ \begin{matrix}    3 & -4  \\    1 & -1  \\ \end{matrix} \right]\], then the value of \[{{X}^{n}}\]is [EAMCET 1991]

    A) \[\left[ \begin{matrix}    3n & -4n  \\    n & -n  \\ \end{matrix} \right]\]

    B) \[\left[ \begin{matrix}    2+n & 5-n  \\    n & -n  \\ \end{matrix} \right]\]

    C) \[\left[ \begin{matrix}    {{3}^{n}} & {{(-4)}^{n}}  \\    {{1}^{n}} & {{(-1)}^{n}}  \\ \end{matrix} \right]\]

    D) None of these

    Correct Answer: D

    Solution :

    \[X=\left[ \begin{matrix}    3 & -4  \\    1 & -1  \\ \end{matrix} \right]\Rightarrow {{X}^{2}}=\left[ \begin{matrix}    5 & -8  \\    2 & -3  \\ \end{matrix} \right]\]. Clearly for\[n=2\], the matrices in (a), (b), (c) do not tally with\[\left[ \begin{matrix}    5 & -8  \\    2 & -3  \\ \end{matrix} \right]\].


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