Integrating by partial fraction.

Click For Summary

Homework Help Overview

The problem involves integrating a rational function using partial fraction decomposition, specifically the integral of the form \(\int \frac{dx}{(x+1)(x^2+1)(x^3+1)}\).

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to solve the integral using different forms of partial fractions, questioning the validity of their approaches when they encounter unexpected results.
  • Some participants discuss the implications of the factorization of the denominator, suggesting that certain terms may not be necessary.
  • There is a proposal to adjust the form of the partial fraction decomposition based on the division of polynomials.

Discussion Status

The discussion is ongoing, with participants exploring various forms of partial fraction decomposition. Some guidance has been offered regarding the structure of the decomposition, but there is no explicit consensus on the best approach yet.

Contextual Notes

Participants are navigating the complexities of polynomial division and the implications for the decomposition of the integrand. There is a sense of uncertainty regarding the necessity of certain terms in the partial fraction setup.

azatkgz
Messages
182
Reaction score
0

Homework Statement



[tex]\int \frac{dx}{(x+1)(x^2+1)(x^3+1)}[/tex]



The Attempt at a Solution



I tried to solve it in 3 ways.
1)[tex]\frac{A}{(x+1)}+\frac{B}{(x^2+1)}+\frac{C}{(x^3+1)}[/tex]

2)[tex]\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C+Ex}{(x^3+1)}[/tex]

3)[tex]\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C+Ex+Fx^2}{(x^3+1)}[/tex]
But it gives me nonsense.
 
Physics news on Phys.org
(x+1) divides (x^3+1). You can write the partial fraction with just linear and quadratic denominators.
 
Then should I solve in this way?

[tex]\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C}{(x+1)^2}+\frac{F+Ex}{(x^2-x+1)}[/tex]
 
That looks ok to me.
 
damn this prob is going to be long
 

Similar threads

Replies
4
Views
2K
Replies
4
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 105 ·
4
Replies
105
Views
11K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K