JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Special types of matrices, Transpose, Adjoint and Inverse of matrices

  • question_answer
    If A is a square matrix for which \[{{a}_{ij}}={{i}^{2}}-{{j}^{2}}\], then  A is   [RPET 1999]

    A) Zero matrix

    B) Unit matrix

    C) Symmetric matrix

    D) Skew symmetric matrix

    Correct Answer: D

    Solution :

    \[{{\log }_{x}}y{{\log }_{y}}x=1\}\] is a square matrix. For a skew symmetric matrix \[\left| \,\begin{matrix}    x+4 & -1+x & 2  \\    0 & -x & x  \\    0 & -x & 0  \\ \end{matrix}\, \right|\,=0\] Þ \[(x+4)\,(0+{{x}^{2}})=0\Rightarrow x=-4,\,0\] and \[{{a}_{ji}}={{j}^{2}}-{{i}^{2}}\] Þ \[{{a}_{ij}}+{{a}_{ji}}=0\Rightarrow \,{{a}_{ij}}=-{{a}_{ji}}\]. Hence, \[{{p}^{-1}}+I+Ip+............+{{p}^{n-1}}I=O.{{p}^{-1}}\] is a skew symmetric matrix.


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