JEE Main & Advanced JEE Main Paper Phase-I (Held on 07-1-2020 Evening)

  • question_answer
    Let \[A=[{{a}_{ij}}]\] and \[B=[{{b}_{ij}}]\] be two \[3\times 3\] real matrices such that \[{{b}_{ij}}={{(3)}^{(i+j2)}}\,{{a}_{ji}},\]where i, j = 1, 2, 3. If the determinant of B is 81, then the determinant of A is         [JEE MAIN Held on 07-01-2020 Evening]

    A) 1/9      

    B) 1/81

    C) 3                     

    D) 1/3

    Correct Answer: A

    Solution :

    [a] \[\therefore \,\,\,{{3}^{4}}={{3}^{6}}\cdot \det \,(A)\] \[\therefore \,\,\,\det \,(A)=\frac{1}{{{3}^{2}}}=\frac{1}{9}\]     

You need to login to perform this action.
You will be redirected in 3 sec spinner