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

  • question_answer
    If \[|{{A}_{n\times n}}|=3\] and \[|adj\,\,A|=243,\] what is the value of n?

    A) \[4\]

    B) \[5\]

    C) \[6\]

    D) \[7\]

    Correct Answer: C

    Solution :

    [c] As given: \[\left| {{A}_{n\times n}} \right|=3\] and \[\left| adj\,\,A \right|=243\] Determinant of adjoint A 13 given by: \[\left| adj\,\,A \right|={{\left| {{A}_{n\times n}} \right|}^{n-1}}\] \[\Rightarrow 243={{3}^{n-1}}\Rightarrow {{3}^{5}}={{3}^{n-1}}\Rightarrow n-1=5\] \[\Rightarrow n=6\]


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