How to Convert an Integral from (1 + x) to 1 - n/(x+n)

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SUMMARY

The discussion focuses on converting the integral from \(\int_0^{x/n} \frac{1}{(1+x)^2} dx\) to the expression \(1 - \frac{n}{x+n}\). The key technique involves using the substitution \(u = 1 + x\) to simplify the integral. Participants emphasize the importance of correctly handling the variable of integration and computing \(\frac{dx}{du}\) during the substitution process. The final result is achieved through algebraic manipulation after performing the integration.

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confused88
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Hi! I'm having trouble understanding my textbook, so can someone please explain to me how they got from


\int1/(1+x)2 dx, with the range of the integral from 0 to x/n

to

1 - n/(x+n)


THank you So MuCh
 
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Are you having trouble with the integration or the final answer?

u substitution works fine here, let u = (1 + x) and integrate. The final answer is a simple algebraic trick, nothing spectacular.
 


I'm just having trouble with the integration ><. Oh wells
 


You're looking for the integral of \mathop \smallint \nolimits_0^{x/n} \frac{1}{{(1 + x&#039;)^2 }}dx&#039; (technically you're not allowed to have your variable of integration in your bounds)

Make a substitution so that your integral now becomes \mathop \smallint \nolimits_0^{x/n} \frac{1}{{(u)^2 }}du\frac{{dx}}{{du}} and remember to compute dx/du.

What, when you take its derivative becomes \frac{1}{{u^2 }}? Find what that is, substitute back in for what you had set u to and you can plug in your integration limits and wala!
 

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