JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Self Evaluation Test - Matrices

  • question_answer
    Let \[A=\left[ \begin{matrix}    0 & \alpha   \\    0 & 0  \\ \end{matrix} \right]\] and \[{{(A+I)}^{50}}-50A=\left[ \begin{matrix}    a & b  \\    c & d  \\ \end{matrix} \right],\]find\[abc+abd+bcd+acd\]   

    A) 0

    B) -1

    C) 1

    D) None of these

    Correct Answer: A

    Solution :

    [a] As \[{{A}^{2}}=0,{{A}^{k}}=0\forall \,k\ge 2\]. Thus, \[{{(A+I)}^{50}}=I+50A\Rightarrow {{(A+I)}^{50}}-50A=I\] \[\therefore a=1,\,b=0,\,c=0,\,d=1\] \[\operatorname{abc} + abd + bcd + acd = 0\]


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