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Question: Answered & Verified by Expert
$\int \frac{e^x}{\left(1+e^x\right)\left(2+e^x\right)} d x=$
MathematicsIndefinite IntegrationJEE Main
Options:
  • A $\log\left[\left(1+e^x\right)\left(2+e^x\right)\right]+c$
  • B $\log \left[\frac{1+e^x}{2+e^x}\right]+c$
  • C $\log \left[\left(1+e^x\right) \sqrt{2+e^x}\right]+c$
  • D None of these
Solution:
2986 Upvotes Verified Answer
The correct answer is: $\log \left[\frac{1+e^x}{2+e^x}\right]+c$
$\int \frac{e^x}{\left(1+e^x\right)\left(2+e^x\right)} d x=\int\left\{\frac{e^x}{1+e^x}-\frac{e^x}{2+e^x}\right\} d x$
Now put $1+e^x=t$ and $2+e^x=t$, then the required integral
$=\log \left(1+e^x\right)-\log \left(2+e^x\right)=\log \left(\frac{1+e^x}{2+e^x}\right)+c .$

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