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The value of ∫{1log⁡ex−1(log⁡ex)2}dx\int \left\{ \frac{1}{\log_e x} - \frac{1}{(\log_e x)^2} \right\} dx is

Solution

✅ Correct Option: 4

Find ∫{1log⁡ex−1(log⁡ex)2}dx\int \left\{ \frac{1}{\log_e x} - \frac{1}{(\log_e x)^2} \right\} dx


Consider y=xlog⁡exy = \frac{x}{\log_e x} and differentiate using the quotient rule.

For y=uvy = \frac{u}{v} where u=xu = x and v=log⁡exv = \log_e x:

dudx=1\frac{du}{dx} = 1

dvdx=1x\frac{dv}{dx} = \frac{1}{x}


Applying the quotient rule:

dydx=log⁡ex⋅(1)−x⋅(1x)(log⁡ex)2\frac{dy}{dx} = \frac{\log_e x \cdot (1) - x \cdot \left(\frac{1}{x}\right)}{(\log_e x)^2}

=log⁡ex−1(log⁡ex)2= \frac{\log_e x - 1}{(\log_e x)^2}


Splitting the fraction:

=log⁡ex(log⁡ex)2−1(log⁡ex)2= \frac{\log_e x}{(\log_e x)^2} - \frac{1}{(\log_e x)^2}

=1log⁡ex−1(log⁡ex)2= \frac{1}{\log_e x} - \frac{1}{(\log_e x)^2}


Since ddx(xlog⁡ex)=1log⁡ex−1(log⁡ex)2\frac{d}{dx}\left(\frac{x}{\log_e x}\right) = \frac{1}{\log_e x} - \frac{1}{(\log_e x)^2}

Therefore:

∫{1log⁡ex−1(log⁡ex)2}dx=xlog⁡ex+c\int \left\{ \frac{1}{\log_e x} - \frac{1}{(\log_e x)^2} \right\} dx = \frac{x}{\log_e x} + c

where cc is an arbitrary constant.

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