JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Expansion of determinants, Solution of equation in the form of determinants and properties of determinants

  • question_answer
    The determinant \[\left| \,\begin{matrix}    4+{{x}^{2}} & -6 & -2  \\    -6 & 9+{{x}^{2}} & 3  \\    -2 & 3 & 1+{{x}^{2}}  \\ \end{matrix}\, \right|\] is not divisible by [J & K 2005]

    A) x

    B) \[{{x}^{3}}\]

    C) \[14+{{x}^{2}}\]

    D) \[{{x}^{5}}\]

    Correct Answer: C

    Solution :

    \[\left| \,\begin{matrix}    4+{{x}^{2}} & -6 & -2  \\    -6 & 9+{{x}^{2}} & 3  \\    -2 & 3 & 1+{{x}^{2}}  \\ \end{matrix} \right|={{x}^{4}}(14+{{x}^{2}})\]\[=x.{{x}^{3}}(14+{{x}^{2}})\] Hence, the determinant is divisible by x,\[{{x}^{3}}\] and \[(14+{{x}^{2}})\], but not divisible by \[{{x}^{5}}\].


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