CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2001

  • question_answer
    The    sum    of    the    series \[{{\log }_{4}}2-{{\log }_{8}}2+{{\log }_{16}}2...\]is:

    A)  \[{{e}^{2}}\]                                     

    B) \[{{\log }_{e}}2+1\]

    C)  \[{{\log }_{e}}3-2\]                        

    D) \[1-{{\log }_{e}}2\]

    Correct Answer: D

    Solution :

    We have \[{{\log }_{4}}2-{{\log }_{8}}2-{{\log }_{16}}2{{\log }_{32}}2+...\] \[=\frac{1}{{{\log }_{2}}4}-\frac{1}{{{\log }_{2}}8}+\frac{1}{{{\log }_{2}}16}-\frac{1}{{{\log }_{2}}32}\] \[\Rightarrow \]\[\frac{1}{2}-\frac{1}{3}+\frac{1}{4}-\frac{1}{5}+...\] \[=1-\left( 1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}... \right)\] \[=1-{{\log }_{e}}2\]


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