BCECE Engineering BCECE Engineering Solved Paper-2008

  • question_answer
    \[\left| \begin{matrix}    \log e & \log {{e}^{2}} & \log {{e}^{3}}  \\    \log {{e}^{2}} & \log {{e}^{3}} & \log {{e}^{4}}  \\    \log {{e}^{3}} & \log {{e}^{4}} & \log {{e}^{5}}  \\ \end{matrix} \right|\]is equal to

    A)  0                            

    B)         1                            

    C)  4 loge                   

    D)         5 loge

    Correct Answer: A

    Solution :

    \[\left| \begin{matrix}    \log e & \log {{e}^{2}} & \log {{e}^{3}}  \\    \log {{e}^{2}} & \log {{e}^{3}} & \log {{e}^{4}}  \\    \log {{e}^{3}} & \log {{e}^{4}} & \log {{e}^{5}}  \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    \log e & 2\log e & 3\log e  \\    2\log e & 3\log e & 4\log e  \\    3\log e & 4\log e & 5\log e  \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    1 & 2 & 3  \\    2 & 3 & 4  \\    3 & 4 & 5  \\ \end{matrix} \right|\] Applying \[{{C}_{2}}\to {{C}_{2}}-{{C}_{1}},{{C}_{3}}\to {{C}_{3}}-{{C}_{2}}\] \[=\left| \begin{matrix}    1 & 1 & 1  \\    2 & 1 & 1  \\    3 & 1 & 1  \\ \end{matrix} \right|\] (\[\because \]Two columns are identical)


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