Evaluating Integral with Partial Fractions: A Numerical Approach

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SUMMARY

The discussion focuses on evaluating the integral \(\int \frac{1}{(x+5)^2(x-1)} dx\) using partial fractions. The user initially derives an expression that differs from the textbook answer, which includes a term \(-\frac{1}{6}\frac{1}{x+5}\). The discrepancy arises from the integration of the term \(-\frac{1/6}{(x+5)^2}\), which the user fails to recognize as yielding a non-logarithmic result. The correct approach involves properly applying partial fraction decomposition and integrating each term accordingly.

PREREQUISITES
  • Understanding of integral calculus, specifically integration techniques.
  • Familiarity with partial fraction decomposition.
  • Knowledge of logarithmic and non-logarithmic antiderivatives.
  • Ability to manipulate algebraic expressions and simplify integrals.
NEXT STEPS
  • Study the process of partial fraction decomposition in detail.
  • Learn how to integrate rational functions involving repeated linear factors.
  • Review the derivation of antiderivatives for functions like \(\frac{1}{x^2}\).
  • Practice solving integrals that involve logarithmic and non-logarithmic terms.
USEFUL FOR

Students and educators in calculus, particularly those focusing on integration techniques and partial fractions. This discussion is beneficial for anyone looking to clarify common pitfalls in evaluating integrals involving rational functions.

colderduck
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Homework Statement


I am supposed to evaluate the integral using partial fractions.
[tex]\int \frac{1}{(x+5)^2(x-1)} dx[/tex]

2. The attempt at a solution

So after doing all the work, I get
[tex](-1/36)ln|x+5| - (13/6)ln|x+5| + (1/36)ln|x-1|[/tex]

But the answer in the book appears as
[tex](-1/36)ln|x+5| - (1/6)\frac{1}{x+5} + (1/36)ln|x-1|[/tex]

Here is what I have before I integrate it.
[tex]\int \frac{-1/36}{x+5} - \frac{1/6}{(x+5)^2} + \frac{1/36}{x-1} dx[/tex]
I assume it has to do with the (x+5)2, but I can't figure out what happened to get that.
 
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Well, there's some sort of sign error involving the term we are concerned with, but disregarding that, the books answer is correct.

What is the antiderivative of 1/x^2 ? I don't see where you pulled a log from.

Welcome to PF btw =] !
 
colderduck said:

Homework Statement


I am supposed to evaluate the integral using partial fractions.
[tex]\int \frac{1}{(x+5)^2(x-1)} dx[/tex]

2. The attempt at a solution

So after doing all the work, I get
[tex](-1/36)ln|x+5| - (13/6)ln|x+5| + (1/36)ln|x-1|[/tex]

But the answer in the book appears as
[tex](-1/36)ln|x+5| - (1/6)\frac{1}{x+5} + (1/36)ln|x-1|[/tex]

Here is what I have before I integrate it.
[tex]\int \frac{-1/36}{x+5} - \frac{1/6}{(x+5)^2} + \frac{1/36}{x-1} dx[/tex]
I assume it has to do with the (x+5)2, but I can't figure out what happened to get that.
Please show how you got that. What partial fractions did you get and how did you integrate each?
 

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