Solving Integral Using Integration by Parts

In summary, the conversation discusses using integration by parts to solve the problem of finding the integral of ln(x+3). The first step is to rewrite the integral as xln(x+3) - integral x/(x+3). The next step is to use long division to simplify the integral of x/(x+3), or to rewrite the numerator as a sum of two integrals.
  • #1
Frillth
80
0
I'm doing a problem where I'm supposed to use integration by parts. I have:

Integral ln(x+3)dx

u=ln(x+3) dv=dx
du=1/(x+3) v=x

integral ln(x+3) = xln(x+3) - integral x/(x+3)

That's as far as I've gotten. I know that I should be able to find the integral of x/(x+3) fairly easily, but I just completely forgot how to do it. Could somebody please lend me a hand?
 
Physics news on Phys.org
  • #2
Do the long division of x / (x + 3). Then you should have an easily integrable result.
 
  • #3
Another option is this: Rewrite your numerator as
[tex] \int \frac{x + 3 - 3}{x + 3} dx[/tex] . Then, you can have two integrals, [tex] \int \frac{x+3}{x+3} dx -3 \int \frac{1}{x+3} dx [/tex]

That should be easier to evaluate. Adding the +3 -3 is the same as adding zero, so it's okay.
 

What is integration by parts?

Integration by parts is a method used in calculus to evaluate integrals of products of functions. It is based on the product rule for differentiation, and involves breaking down an integral into smaller parts that can be more easily solved.

What are the steps for solving an integral using integration by parts?

The steps for solving an integral using integration by parts are as follows:
1. Identify the function to be integrated and the function to be differentiated.
2. Use the product rule to rewrite the integral in a simpler form.
3. Choose which function to integrate and which to differentiate.
4. Evaluate the resulting integral.
5. Repeat the process until the integral can be solved.

When should I use integration by parts?

Integration by parts is most useful when the integral involves a product of functions, and neither function can be easily integrated using traditional methods. It is also helpful when the integral involves an inverse trigonometric function.

What are some common mistakes to avoid when using integration by parts?

Some common mistakes to avoid when using integration by parts include:
- Forgetting to choose which function to integrate and differentiate.
- Not applying the product rule correctly.
- Forgetting to include the constant of integration.
- Not simplifying the integral after each iteration.

Can I use integration by parts to solve definite integrals?

Yes, integration by parts can be used to solve definite integrals. After each iteration, the limits of integration must be applied to the resulting integral. The final answer will be a numerical value.

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
987
  • Calculus and Beyond Homework Help
Replies
15
Views
774
  • Calculus and Beyond Homework Help
Replies
22
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
925
  • Calculus and Beyond Homework Help
Replies
2
Views
415
  • Calculus and Beyond Homework Help
Replies
9
Views
744
  • Calculus and Beyond Homework Help
Replies
3
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
600
  • Calculus and Beyond Homework Help
Replies
5
Views
321
  • Calculus and Beyond Homework Help
Replies
1
Views
481
Back
Top