Evaluate $\int \left\{ \frac{1}{\log x} - \frac{1}{(\log x)^2} \right\} dx$ (where $x > 1$). |
$x \log x + C$ $\frac{\log x}{x} + C$ $\frac{x}{\log x} + C$ $x^2 \log x + C$ |
$\frac{x}{\log x} + C$ |
The correct answer is Option (3) → $\frac{x}{\log x} + C$ $\int \left\{ \frac{1}{\log x} - \frac{1}{(\log x)^2} \right\} dx$ $= \int \frac{1}{\log x} dx - \int \frac{1}{(\log x)^2} dx$ $= \frac{1}{\log x} \cdot \int 1 dx - \int \left\{ \frac{d}{dx} \left( \frac{1}{\log x} \right) \int 1 dx \right\} dx - \int \frac{1}{(\log x)^2} dx$ $= \frac{x}{\log x} + \int \frac{1}{(\log x)^2} \cdot \frac{1}{x} \cdot x dx - \int \frac{1}{(\log x)^2} dx$ $= \frac{x}{\log x} + \int \frac{1}{(\log x)^2} dx - \int \frac{1}{(\log x)^2} dx$ $= \frac{x}{\log x} + C$ |