CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2005

  • question_answer
    The inverse of the matrix \[\left[ \begin{matrix}    5 & -2  \\    3 & 1  \\ \end{matrix} \right]\] is :

    A)  \[\frac{1}{11}\left[ \begin{matrix}    1 & 2  \\    -3 & 5  \\ \end{matrix} \right]\]                   

    B)  \[\left[ \begin{matrix}    1 & 2  \\    -3 & 5  \\ \end{matrix} \right]\]

    C)  \[\frac{1}{13}\left[ \begin{matrix}    -2 & 5  \\    1 & 3  \\ \end{matrix} \right]\]                   

    D)  \[\left[ \begin{matrix}    1 & 3  \\    -2 & 5  \\ \end{matrix} \right]\]

    Correct Answer: A

    Solution :

    Let \[A=\left[ \begin{matrix}    5 & -2  \\    3 & 1  \\ \end{matrix} \right]\] \[|A|=5+6=11\] and adj. \[A=\left[ \begin{matrix}    1 & 2  \\    -3 & 5  \\ \end{matrix} \right]\]                 \[{{A}^{-1}}=\frac{1}{|A|}\] (adj. A)                 \[=\frac{1}{11}\left[ \begin{matrix}    1 & 2  \\    -3 & 5  \\ \end{matrix} \right]\]


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