CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2008

  • question_answer
    If \[A=\left| \begin{matrix}    {{a}_{1}} & {{b}_{1}} & {{c}_{1}}  \\    {{a}_{2}} & {{b}_{2}} & {{c}_{2}}  \\    {{a}_{3}} & {{b}_{3}} & {{c}_{3}}  \\ \end{matrix} \right|\]  and \[B=\left| \begin{matrix}    {{c}_{1}} & {{c}_{2}} & {{c}_{3}}  \\    {{a}_{1}} & {{a}_{2}} & {{a}_{3}}  \\    {{b}_{1}} & {{b}_{2}} & {{b}_{3}}  \\ \end{matrix} \right|,\] then

    A)  \[A=-B\]                             

    B)  \[A=B\]

    C)  \[B=0\]                               

    D)  \[B={{A}^{2}}\]

    Correct Answer: B

    Solution :

    Let   \[[A]=\left[ \begin{matrix}    {{a}_{1}} & {{b}_{1}} & {{c}_{1}}  \\    {{a}_{2}} & {{b}_{2}} & {{c}_{2}}  \\    {{a}_{3}} & {{b}_{3}} & {{c}_{3}}  \\ \end{matrix} \right]\]and \[[B]=\left[ \begin{matrix}    {{c}_{1}} & {{c}_{2}} & {{c}_{3}}  \\    {{a}_{1}} & {{a}_{2}} & {{a}_{3}}  \\    {{b}_{1}} & {{b}_{2}} & {{b}_{3}}  \\ \end{matrix} \right]=\left[ \begin{matrix}    {{a}_{1}} & {{a}_{2}} & {{a}_{3}}  \\    {{b}_{1}} & {{b}_{2}} & {{b}_{3}}  \\    {{c}_{1}} & {{c}_{2}} & {{c}_{3}}  \\ \end{matrix} \right]\]                 \[={{[A]}^{t}}\] As we know, det \[(A)=det\,(A')\] \[\therefore \]  \[A=B\]


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