JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Special types of matrices, Transpose, Adjoint and Inverse of matrices

  • question_answer
    If \[A=\left[ \begin{matrix}    2 & 2  \\    -3 & 2  \\ \end{matrix} \right]\] and \[B=\left[ \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right],\] then \[{{({{B}^{-1}}{{A}^{-1}})}^{-1}}\]=  [EAMCET 2001]

    A) \[\left[ \begin{matrix}    2 & -2  \\    2 & 3  \\ \end{matrix} \right]\]

    B) \[\left[ \begin{matrix}    3 & -2  \\    2 & 2  \\ \end{matrix} \right]\]

    C) \[\frac{1}{10}\left[ \begin{matrix}    2 & 2  \\    -2 & 3  \\ \end{matrix} \right]\]

    D) \[\frac{1}{10}\left[ \begin{matrix}    3 & 2  \\    -2 & 2  \\ \end{matrix} \right]\]

    Correct Answer: A

    Solution :

    \[{{({{B}^{-1}}{{A}^{-1}})}^{-1}}={{({{A}^{-1}})}^{-1}}{{({{B}^{-1}})}^{-1}}=AB\] (Reversal law of inverses) \[=\,\left[ \,\begin{matrix}    2 & 2  \\    -3 & 2  \\ \end{matrix}\, \right]\,\left[ \,\begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix}\, \right]=\left[ \,\begin{matrix}    2 & -2  \\    2 & 3  \\ \end{matrix}\, \right]\].


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