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

  • question_answer
    The inverse of a matrix \[A=\left( \begin{matrix}    a & b  \\    c & d  \\ \end{matrix} \right)\]is  [AMU 2001]

    A) \[\left( \begin{matrix}    d & -b  \\    -c & a  \\ \end{matrix} \right)\]

    B) \[\frac{1}{(ad-bc)}\left( \begin{matrix}    d & -b  \\    -c & a  \\ \end{matrix} \right)\]

    C) \[\frac{1}{|A|}\left( \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right)\]

    D) \[\left( \begin{matrix}    b & -a  \\    d & -c  \\ \end{matrix} \right)\]

    Correct Answer: B

    Solution :

    \[|A|\,=(ad-bc)\] \[\therefore \,\,{{A}^{-1}}=\frac{1}{(ad-bc)}\,\,\left[ \,\begin{matrix}    d & -b  \\    -c & a  \\ \end{matrix} \right]\].


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