CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    \[\int{\frac{1}{x}({{\log }_{ex}}e)}dx\]is equal to

    A)  \[{{\log }_{e}}(1-{{\log }_{e}}x)+c\]

    B)  \[{{\log }_{e}}({{\log }_{e}}ex-1)+c\]

    C)  \[{{\log }_{e}}({{\log }_{e}}x-1)+c\]

    D)  \[{{\log }_{e}}({{\log }_{e}}x+x)+c\]

    E)  \[{{\log }_{e}}(1+{{\log }_{e}}x)+c\]

    Correct Answer: E

    Solution :

    Let \[I=\int{\frac{1}{x}}({{\log }_{ex}}e)dx\] \[=\int{\frac{1}{x(1+{{\log }_{e}}x)}}dx\] Put \[{{\log }_{e}}x=t\Rightarrow \frac{1}{x}dx=dt\] \[\therefore \]  \[I=\int{\frac{dt}{(1+t)}}\]                 \[={{\log }_{e}}(1+t)+c\]                 \[={{\log }_{e}}(1+{{\log }_{e}}x)+c\]


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