10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    The expansion of log \[{{\log }_{e}}\frac{1}{(1-x)}\]is

    A)  \[x-\frac{{{x}^{2}}}{2}+\frac{{{x}^{3}}}{3}-\,.....\]

    B)         \[x+\frac{{{x}^{2}}}{2}+\frac{{{x}^{3}}}{3}+\,.....\]  

    C)  \[1-x+\frac{{{x}^{2}}}{2}-\frac{{{x}^{3}}}{3}+\,.....\]

    D)        \[1+x-\frac{{{x}^{2}}}{2}+\frac{{{x}^{3}}}{3}-\,.....\]

    Correct Answer: B

    Solution :

                    \[{{\log }_{e}}\frac{1}{(1-x)}={{\log }_{e}}{{(1-x)}^{-1}}=-{{\log }_{e}}^{(1-x)}\]                 \[=-\left[ -x-\frac{{{x}^{2}}}{2}-\frac{{{x}^{3}}}{3}-\frac{{{x}^{4}}}{4}-...\infty  \right]\]                 \[=x+\frac{{{x}^{2}}}{2}+\frac{{{x}^{3}}}{3}+...\infty \]


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