JEE Main & Advanced JEE Main Paper (Held On 9 April 2014)

  • question_answer
    If B is a \[3\times 3\]matrix such that \[{{B}^{2}}=0,\]then det. \[[{{(I+B)}^{50}}-50B]\]is equal to:     [JEE Main Online Paper ( Held On 09 Apirl  2014  )

    A) 1             

    B) 2

    C) 3                                             

    D) 50

    Correct Answer: A

    Solution :

                    \[\det {{[(I+B)]}^{50}}-50B]\] \[=\det {{[}^{50}}{{C}_{0}}I{{+}^{50}}{{C}_{1}}B{{+}^{50}}{{C}_{2}}{{B}^{2}}{{+}^{50}}{{C}_{3}}{{B}^{3}}+...\] \[{{+}^{50}}{{C}_{50}}{{B}^{50}}{{B}^{50}}-50B]\] {All terms having \[{{B}^{n}},2\le n\le 50\]will be zero because given that B2 = 0} \[=\det [I+50B-50B]=det[I]=1\]                                


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