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Value of ∫(1logx−1(logx)2)dx\int \left(\frac{1}{logx} - \frac{1}{(logx)^2}\right)dx is

Solution

✅ Correct Option: 1

When an integral appears complicated, checking if any candidate function has the given expression as its derivative can be efficient.

Consider xlog⁡x\frac{x}{\log x} as a candidate for the antiderivative.


Using the quotient rule where u=xu = x and v=log⁡xv = \log x:

u′=1u' = 1

v′=1xv' = \frac{1}{x}


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

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

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

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


This matches the integrand exactly.

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

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