Question:medium

\(\displaystyle\int e^{x}\left(\log x+\frac{1}{x^{2}}\right)dx\) is equal to
(consider \(\log_e x = \log x\))

Show Hint

Write the integrand as \(e^{x}[f(x)+f^{\prime}(x)]\) with \(f(x)=\log x-\frac{1}{x}\).
Updated On: Oct 1, 2026
  • \(e^{x}\log_e x + c\) : where c is an arbitrary constant
  • \(e^{x}\left(\log_e x+\frac{1}{x}\right)+c\): where c is an arbitrary constant
  • \(e^{x}\left(\log_e x-\frac{1}{x}\right)+c\): where c is an arbitrary constant
  • \(e^{x}\cdot\frac{1}{x}+c\) : where c is an arbitrary constant
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Plan.
Instead of guessing a function, we will use integration by parts and see what remains. Split the integral as $\int e^{x}\log x\,dx+\int \frac{e^{x}}{x^{2}}dx$.

Step 2: Parts on the first piece.
Take $u=\log x$ and $dv=e^{x}dx$. Then $du=\frac{dx}{x}$ and $v=e^{x}$.
\[ \int e^{x}\log x\,dx = e^{x}\log x-\int \frac{e^{x}}{x}dx \]

Step 3: Parts on the second piece.
Take $u=e^{x}$ and $dv=\frac{dx}{x^{2}}$. Then $du=e^{x}dx$ and $v=-\frac{1}{x}$.
\[ \int \frac{e^{x}}{x^{2}}dx = -\frac{e^{x}}{x}+\int \frac{e^{x}}{x}dx \]

Step 4: Add the two results.
The unknown integral $\int \frac{e^{x}}{x}dx$ appears with opposite signs, so it cancels.
\[ \int e^{x}\left(\log x+\frac{1}{x^{2}}\right)dx = e^{x}\log x-\frac{e^{x}}{x}+c \]

Step 5: Match with the options.
We can write the result as $e^{x}\left(\log x-\frac{1}{x}\right)+c$. Option 3 has exactly this form. Options 1, 2 and 4 have a different sign or miss a term, so they do not match.

Final Answer:
Option 3 is correct. \[ \boxed{e^{x}\left(\log x-\frac{1}{x}\right)+c} \]
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