Question:medium

If \(f(x) = \frac{1}{logx}\) and \(g(x) = \frac{1}{(logx)^2}\), then the value of \(\int [f(x)-g(x)]\,dx\) is...

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The expression is the derivative of x/log x.
Updated On: Oct 1, 2026
  • \((logx)^2+c\)
  • \(xlogx+c\)
  • \(\frac{x}{logx}+c\)
  • \(\frac{1}{logx}+c\)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: By Parts:
Compute $\int\dfrac{dx}{\log x}$ by parts with $u=\dfrac1{\log x}$ and $dv=dx$: it equals $\dfrac x{\log x}+\int\dfrac{dx}{(\log x)^2}$.

Step 2: Subtract:
The derivative of $\dfrac1{\log x}$ is $-\dfrac1{x(\log x)^2}$, and multiplying by $x$ gives $-\dfrac1{(\log x)^2}$. Subtracting $-$(that integral) in the by-parts formula gives the plus sign above. Moving the integral to the left side:
\[ \int\frac{dx}{\log x}-\int\frac{dx}{(\log x)^2}=\frac{x}{\log x}+c \]

Step 3: Answer:
The result is $\dfrac{x}{\log x}+c$. Option (C).

Final Answer:
Option (C). \[ \boxed{\text{(C) } \frac{x}{\log x}+c} \]
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