JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Types of matrices, Algebra of matrices

  • question_answer
    If \[A=\left[ \begin{matrix}    3 & -5  \\    -4 & 2  \\ \end{matrix} \right],\]then \[{{A}^{2}}-5A=\] [RPET 2002]

    A) I

    B) 14 I

    C) 0

    D) None of these

    Correct Answer: B

    Solution :

    \[{{A}^{2}}=A.A=\left[ \begin{matrix}    3 & -5  \\    -4 & 2  \\ \end{matrix} \right]\text{ }\left[ \begin{matrix}    3 & -5  \\    -4 & 2  \\ \end{matrix} \right]\] \[\Rightarrow \,{{A}^{2}}=\left[ \begin{matrix}    29 & -25  \\    -20 & 24  \\ \end{matrix} \right]\] and \[5A=\left[ \begin{matrix}    15 & -25  \\    -20 & 10  \\ \end{matrix} \right]\] \ \[{{A}^{2}}-5A=14\left[ \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right]=14I\].


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