How can I integrate these two challenging expressions?

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Discussion Overview

The discussion revolves around two integration problems involving rational functions and trigonometric identities. Participants explore methods for integrating the expressions, including factoring and substitution techniques.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents two integration questions, expressing difficulty in finding suitable substitutions.
  • Another participant suggests factoring the first expression to simplify the integration process.
  • A later reply identifies the factorization of the first expression as (x + 4)(x - 4) and proposes pulling out a constant to simplify the integral.
  • Another participant confirms the approach of factoring and notes that the integral will be scaled by a factor of 1/2.
  • For the second integral, a participant suggests using a substitution of u = 3x and considering the derivative of arctan(u) as a potential method.
  • One participant mentions attempting to use a trigonometric identity but indicates that it did not yield the desired results.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the best approach for either integration problem, and multiple methods are being discussed without resolution.

Contextual Notes

Participants express uncertainty about the effectiveness of their proposed methods, particularly regarding the second integral and the use of trigonometric identities.

Joza
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I need help on these two integration questions:

1.

(x^2 -16)/(2x + 8) dx


2.

1/(1+9x^2) dx


I can't seem to find a "u" for either. And I tried a tan identity on number 2 to no avail.
 
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Did you try factoring the first one?
 
OH WAIT...

Yea so x^2 - 16 would be (x + 4)(x - 4).

Then I can pull a 1/2 outside, and I'll be left with (x + 4) on the bottom. That will cancel out, so it will be the integral of (x - 4)?
 
Well, because of that 1/2 you "pulled outside", it will be (1/2) the integral of x-4.

As far as the second is concerned, you might try letting u= 3x and then think about the derivative of arctan u.
 
Yea that's what I meant.

Well I tried using 1/(1^2 + (3x)^2)...but that didnt work.
 

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