JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2005

  • question_answer
        \[\int{\frac{dx}{x({{x}^{n}}+1)}}\]is equal to:

    A)  \[\frac{1}{n}\log \left( \frac{{{x}^{n}}}{{{x}^{n}}+1} \right)+c\]

    B)  \[\frac{1}{n}\log \left( \frac{{{x}^{n}}+1}{{{x}^{n}}} \right)+c\]

    C)  \[\log \left( \frac{{{x}^{n}}}{{{x}^{n}}+1} \right)+c\]

    D)  none of these

    Correct Answer: A

    Solution :

                    \[\int{\frac{dx}{x({{x}^{n}}+1)}}\] Putting \[{{x}^{n}}+1=t\]                 \[n{{x}^{n-1}}dx=dt\]                 \[=\frac{1}{n}\int{\frac{dt}{t(t-1)}}\]                 \[=\frac{1}{n}\int{\left( \frac{1}{t-1}-\frac{1}{t} \right)}dt\]                 \[=\frac{1}{n}\log \left( \frac{t-1}{t} \right)+c\]                 \[=\frac{1}{n}\log \left( \frac{{{x}^{n}}}{{{x}^{n}}+1} \right)+c\]


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