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

  • question_answer
    If the matrix \[AB=O\], then [Pb. CET 2000]

    A) \[A=O\] or \[B=O\]

    B) \[A=O\] and \[B=O\]

    C) It is not necessary that either \[A=O\]or \[B=O\]

    D) \[A\ne O,B\ne O\]

    Correct Answer: C

    Solution :

    \[AB=O\,\,\,\Rightarrow \,\,|AB|\,=\,0\] Þ \[|A|\,.\,|B|=0\]  Þ  \[|A|\,=\,0\] or \[|B|\,=\,0\] When AB = O, neither A nor B may be O. For example if \[A=\left[ \begin{matrix}    1 & 0  \\    0 & 0  \\ \end{matrix} \right]\] and\[B=\left[ \begin{matrix}    0 & 0  \\    1 & 0  \\ \end{matrix} \right]\], then \[AB=\left[ \begin{matrix}    0 & 0  \\    0 & 0  \\ \end{matrix} \right]\].


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