JEE Main & Advanced Sample Paper JEE Main Sample Paper-37

  • question_answer
    The trace \[{{T}_{r}}(A)\] of a \[3\times 3\] matrix \[A=({{a}_{ij}})\] is defined by the\[{{T}_{r}}(A)={{a}_{11}}+{{a}_{22}}+{{a}_{33}}(i.e.,\,\,{{T}_{r}}(A)\]diagonal elements). Which of the following statements cannot hold?

    A) \[{{T}_{r}}(kA)=k{{T}_{r}}(A)\]\[(k\]is a scalar)

    B) \[{{T}_{r}}(A+B)={{T}_{r}}(A)+{{T}_{r}}(B)\]

    C) \[{{T}_{r}}({{I}_{3}})=A\]

    D) \[{{T}_{r}}({{A}^{2}})={{T}_{r}}{{(A)}^{2}}\]

    Correct Answer: D

    Solution :

     [a]\[{{T}_{r}}(kA)=k({{a}_{11}}+{{a}_{22}}+{{a}_{33}})=k{{T}_{r}}(1)\] [b]\[{{T}_{r}}(A+B)={{a}_{11}}+{{b}_{11}}+{{a}_{22}}+{{b}_{22}}+{{a}_{33}}+{{b}_{33}}\]\[={{T}_{r}}(1)+{{T}_{r}}(2)\] [c]\[{{T}_{r}}({{I}_{3}})=1+1+1=3\] [d]\[{{T}_{r}}({{A}^{2}})=\Sigma a_{11}^{2}+\Sigma a_{12}^{2}\ne {{({{a}_{11}}+{{a}_{22}}+{{a}_{33}})}^{2}}\]


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