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
    \[\left| \,\begin{matrix}    {{({{a}^{x}}+{{a}^{-x}})}^{2}} & {{({{a}^{x}}-{{a}^{-x}})}^{2}} & 1  \\    {{({{b}^{x}}+{{b}^{-x}})}^{2}} & {{({{b}^{x}}-{{b}^{-x}})}^{2}} & 1  \\    {{({{c}^{x}}+{{c}^{-x}})}^{2}} & {{({{c}^{x}}-{{c}^{-x}})}^{2}} & 1  \\ \end{matrix}\, \right|=\][UPSEAT 2002; AMU 2005]

    A) 0

    B) \[2abc\]

    C) \[{{a}^{2}}{{b}^{2}}{{c}^{2}}\]

    D) None of these

    Correct Answer: A

    Solution :

    Put \[-10x+90-42-81+42+9x=0\,\,\text{or}\,\text{ }x=9\] which gives answer (a).


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