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

  • question_answer
    If A and B are \[3\times 3\]matrices such that \[AB=A\] and \[BA=B\], then [Orissa JEE 2003]

    A) \[{{A}^{2}}=A\]and \[{{B}^{2}}\ne B\]

    B) \[{{A}^{2}}\ne A\]and \[{{B}^{2}}=B\]

    C) \[{{A}^{2}}=A\]and \[{{B}^{2}}=B\]

    D) \[{{A}^{2}}\ne A\]and \[{{B}^{2}}\ne B\]

    Correct Answer: C

    Solution :

    Given\[AB=A\], \ \[B=I\]  Þ \[BA=B,\] \[\therefore \] A = I. Hence, \[\Rightarrow \] and\[\left[ \begin{matrix}    1 & -\left( \frac{x+y}{1+xy} \right)  \\    -\left( \frac{x+y}{1+xy} \right) & 1  \\ \end{matrix} \right]\].


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