Evaluating Integral with Partial Fractions: A Numerical Approach

In summary, the conversation is discussing how to evaluate the integral \int \frac{1}{(x+5)^2(x-1)} dx using partial fractions. The original solution obtained by the person had a sign error, but the correct answer is (-1/36)ln|x+5| - (1/6)\frac{1}{x+5} + (1/36)ln|x-1|. The person is confused about where the term involving a logarithm came from, and is asking for clarification on the steps to integrate each partial fraction.
  • #1
colderduck
1
0

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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  • #2
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 =] !
 
  • #3
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?
 

What is the purpose of evaluating integrals with partial fractions?

The purpose of evaluating integrals with partial fractions is to break down complex rational functions into simpler fractions that can be integrated using basic integration techniques.

What is a numerical approach to evaluating integrals with partial fractions?

A numerical approach involves using numerical methods, such as Simpson's rule or the trapezoidal rule, to approximate the value of an integral. This is often used when the integral cannot be evaluated using traditional methods.

What are the steps involved in evaluating integrals with partial fractions using a numerical approach?

The steps involved in evaluating integrals with partial fractions using a numerical approach include: (1) breaking down the rational function into partial fractions, (2) setting up the integral using the partial fractions, (3) choosing a numerical method and determining the appropriate number of subintervals, (4) evaluating the integral using the chosen method, and (5) checking the accuracy of the approximation.

Are there any limitations to using a numerical approach for evaluating integrals with partial fractions?

Yes, there are limitations to using a numerical approach. One limitation is that the method may not provide an exact solution, but rather an approximation. Another limitation is that numerical methods can be computationally intensive and may require a large number of subintervals to achieve an accurate result.

When should a numerical approach be used for evaluating integrals with partial fractions?

A numerical approach should be used when the integral cannot be evaluated using traditional methods, such as u-substitution or integration by parts. It may also be used when an exact solution is not necessary and an approximation is sufficient.

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