Integrating Partial Fractions with a Twist: (x + 3) vs (x - 3)

In summary, there was confusion about the term ##\frac 1 {x - 3}## in the given problem, with some discussing an earlier mistake that might have led to the fractions. However, it was determined that the correct denominator for the second integral should be (x + 3) instead of (x - 3), which is closer to the expected result but still has a small discrepancy. It was also noted that using (x - 3) as the denominator does not work with the given limits, potentially indicating an error in the question.
  • #1
maxim07
53
8
Homework Statement
Question states that integral of given partial fraction is supposed to equal ln(2/sqrt(3)), but I have tried it and it does not seem to. I believe I have integrated correctly, but maybe it can be simplified in such a way to become ln(2/sqrt(2))
Relevant Equations
Partial fraction to integrate = 5/7(2x+1) + 1/7(x-3)
BA7B67FF-82D5-4E6A-9ADA-D5F9C75ACAD2.jpeg
 
Physics news on Phys.org
  • #2
What happened to the term with ##\frac 1 {x - 3}##?

Are you sure there isn't an earlier mistake that led to those fractions?
 
  • #3
This is how I go the reactions -pretty sure it’s right
C490592A-7A97-44F8-B669-B4ECA3DDC9A7.jpeg
 
  • #4
The second term is problem with those limits of integration - in particular at ##x = 3##. You can't make that go away.
 
  • Like
Likes docnet
  • #5
the denominator of your second integral is (x + 3) not (x - 3) as in the question. The version with (x + 3) is closer to ln(2/sqrt(3) but still differs by about 2.4 x 10^-3.

using (x - 3) does not work since using the limits given the term becomes ln|-1| and ln(0) so maybe there is something wrong with the question
 

What is partial fraction integration?

Partial fraction integration is a method used in calculus to break down a complex rational function into simpler fractions that can be integrated separately. It is often used to solve integrals involving polynomials.

When is partial fraction integration used?

Partial fraction integration is typically used when the integrand (the function being integrated) is a rational function, meaning it is a ratio of two polynomials. It can also be used to solve improper integrals or when other integration techniques, such as substitution, are not applicable.

How do you perform partial fraction integration?

To perform partial fraction integration, you first need to factor the denominator of the rational function into linear and irreducible quadratic factors. Then, you set up a system of equations using the coefficients of the factors and solve for the unknown constants. Finally, you integrate each fraction separately and combine the results to get the final answer.

What are the different types of partial fractions?

There are two main types of partial fractions: proper fractions and improper fractions. Proper fractions have a degree of the numerator that is less than the degree of the denominator, while improper fractions have a degree of the numerator that is equal to or greater than the degree of the denominator.

What are some common mistakes to avoid when using partial fraction integration?

Some common mistakes to avoid when using partial fraction integration include not factoring the denominator correctly, making errors in setting up the system of equations, and not checking for extraneous solutions. It is also important to check your final answer by differentiating it to ensure that it is equivalent to the original integrand.

Similar threads

  • Calculus and Beyond Homework Help
Replies
8
Views
949
  • Calculus and Beyond Homework Help
Replies
6
Views
72
  • Calculus and Beyond Homework Help
Replies
16
Views
2K
  • Calculus and Beyond Homework Help
Replies
4
Views
740
  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
549
  • Calculus and Beyond Homework Help
Replies
8
Views
176
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
914
  • Calculus and Beyond Homework Help
Replies
3
Views
772
Back
Top