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

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Discussion Overview

The discussion revolves around the process of converting an integral from the form \(\int \frac{1}{(1+x)^2} \, dx\) with limits from 0 to \(\frac{x}{n}\) to the expression \(1 - \frac{n}{x+n}\). Participants are exploring integration techniques, specifically substitution methods, and clarifying the steps involved in the integration process.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses confusion about the integration process and the final result.
  • Another participant suggests that u-substitution is an effective method for solving the integral, indicating that the final answer involves a simple algebraic manipulation.
  • A further reply emphasizes the importance of correctly setting the variable of integration and adjusting the limits accordingly when making substitutions.
  • Participants discuss the need to compute the derivative of the substitution and how it relates to the integral being solved.

Areas of Agreement / Disagreement

Participants generally agree on the use of u-substitution as a method for solving the integral, but there is no consensus on the clarity of the integration process or the final expression derived from it.

Contextual Notes

Some participants note the technicality of having the variable of integration in the bounds, which may lead to confusion. There are also references to the need for careful computation of derivatives during the substitution process.

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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