J & K CET Engineering J and K - CET Engineering Solved Paper-2015

  • question_answer
    If M is a \[3\times 3\]skew symmetric matrix, then det (M)is

    A)  \[-1\]    

    B)  \[0\]

    C)  \[4\]     

    D)  \[1\]

    Correct Answer: B

    Solution :

    Given, M is a \[3\times 3\]skew symmetric matrix. Let \[M=\left[ \begin{matrix}    0 & -a & -b  \\    a & 0 & -c  \\    b & c & 0  \\ \end{matrix} \right]\] Then, \[\det \,(M)=0\left| \begin{matrix}    0 & -c  \\    c & 0  \\ \end{matrix} \right|+a\left| \begin{matrix}    a & -c  \\    b & 0  \\ \end{matrix} \right|-b\left| \begin{matrix}    a & 0  \\    b & c  \\ \end{matrix} \right|\] \[\Rightarrow \] \[\det \,(M)=a(0+bc)-b(ac-0)\] \[=abc-abc\] \[\Rightarrow \] \[\det \,(M)=0\]


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