J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    The value of the determinant \[\left| \begin{matrix}    0 & {{b}^{3}}-{{a}^{3}} & {{c}^{3}}-{{a}^{3}}  \\    {{a}^{3}}-{{b}^{3}} & 0 & {{c}^{3}}-{{b}^{3}}  \\    {{a}^{3}}-{{c}^{3}} & {{b}^{3}}-{{c}^{3}} & 0  \\ \end{matrix} \right|\]is equal to

    A)  \[{{a}^{3}}-{{b}^{3}}-{{c}^{3}}\]

    B)  \[{{a}^{3}}-{{b}^{3}}-{{c}^{3}}\]

    C)  \[0\]

    D)  \[-{{a}^{3}}+{{b}^{3}}+{{c}^{3}}\]

    Correct Answer: C

    Solution :

    \[\left| \begin{matrix}    0 & {{b}^{3}}-{{a}^{3}} & {{c}^{3}}-{{a}^{3}}  \\    {{a}^{3}}-{{b}^{3}} & 0 & {{c}^{3}}-{{b}^{3}}  \\    {{a}^{3}}-{{c}^{3}} & {{b}^{3}}-{{c}^{3}} & 0  \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    0 & -({{a}^{3}}-{{b}^{3}}) & -({{a}^{3}}-{{c}^{3}})  \\    {{a}^{3}}-{{b}^{3}} & 0 & -({{b}^{3}}-{{c}^{3}})  \\    {{a}^{3}}-{{c}^{3}} & {{b}^{3}}-{{c}^{3}} & 0  \\ \end{matrix} \right|\] \[=({{a}^{3}}-{{b}^{3}})[0+({{b}^{3}}-{{c}^{2}})({{a}^{3}}-{{c}^{3}})]\] \[-({{a}^{3}}-{{c}^{3}})[({{b}^{3}}-{{c}^{3}})({{a}^{3}}-{{b}^{3}})-0]\] \[=({{a}^{3}}-{{b}^{3}})({{b}^{3}}-{{c}^{3}})({{a}^{3}}-{{c}^{3}})\] \[-({{a}^{3}}-{{c}^{3}})({{b}^{3}}-{{c}^{3}})({{a}^{3}}-{{b}^{3}})\] \[=0\]


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