JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Mock Test - Matrices

  • question_answer
    Let A be an nth-order square matrix and B be its adjoint, then \[\left| AB+K{{I}_{n}} \right|\]is (where K is a scalar quantity)

    A)  \[{{(\left| A \right|+K)}^{n-2}}\]         

    B)  \[{{(\left| A \right|+K)}^{n}}\]

    C)  \[{{(\left| A \right|+K)}^{n-1}}\]         

    D)  none of these

    Correct Answer: B

    Solution :

    [b] We have, AB = A(adj A)\[=\left| A \right|{{I}_{n}}\] \[\therefore AB+K{{I}_{n}}=\left| A \right|{{I}_{n}}+K{{I}_{n}}=(\left| A \right|+k){{I}_{n}}\] \[\Rightarrow \left| AB+K{{I}_{n}} \right|=\left| (\left| A \right|+K){{I}_{n}} \right|\]       (\[\therefore \left| \alpha {{I}_{n}} \right|={{\alpha }^{n}}\]) \[={{(\left| A \right|+K)}^{n}}\]


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