RAJASTHAN ­ PET Rajasthan PET Solved Paper-2007

  • question_answer
    If\[{{A}^{2}}-A+I=O,\]then inverse of A is

    A)  \[A+I\]             

    B)  A

    C)  \[A-I\]             

    D)  \[I-A\]

    Correct Answer: D

    Solution :

     Given, \[{{A}^{2}}-A+I=O\] \[\Rightarrow \] \[{{A}^{-1}}{{A}^{2}}-{{A}^{-1}}.A+{{A}^{-1}}I=O\] \[\Rightarrow \] \[({{A}^{-1}}A).A-({{A}^{-1}}.A)+{{A}^{-1}}=0\] \[\Rightarrow \] \[A-I+{{A}^{-1}}=O\] \[\Rightarrow \] \[{{A}^{-1}}=I-A\]


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