U substitution or substitution by parts?

In summary, the conversation is about solving the integral of e^√x/√x dx and the question of whether to use u substitution or integration by parts. It is determined that u substitution would be the best approach, and the integration is simplified to 1/2 ∫〖e^u du〗. The use of brackets and parentheses in the conversation is discussed as well.
  • #1
mickellowery
69
0

Homework Statement


∫〖e^√x/√x dx〗
would this be a u substitution or a substitution by parts?

Homework Equations





The Attempt at a Solution

 
Physics news on Phys.org
  • #2
I would go with an ordinary substitution. The other technique you mentioned is usually called integration by parts.
 
  • #3
oh oops I meant to say integration by parts. So would I let u= sqrt(x)?
 
  • #4
That would be a good thing to try. What does that lead to?
 
  • #5
So if u= sqrt(x) du= 1/2 x^-1/2 and now I'm a little lost because the du doesn't look like it helps me.
 
  • #6
Better written as

[tex]du = \frac 1 {2\sqrt x}\, dx[/tex]

Now take a look at what you are supposed to integrate. Does the integrand involve anything that looks like the above?
 
  • #7
Alright I think I see it but I want to check. Would I write it as 1/2 ∫〖e^u du〗?
 
  • #8
Yes.

BTW, what's the deal with the brackets and parentheses?
 
  • #9
Thanks so much for your help DH. I don't know the deal with the brackets and parentheses. I have been using microsoft word's equation writer because I'm not too sure how to use the equation writer on here. Thanks again!
 

FAQ: U substitution or substitution by parts?

What is the purpose of using U substitution in integration?

U substitution is a technique used in integration to simplify the integrand and make it easier to solve. It involves replacing a complicated expression in the integrand with a simpler variable, U, and then integrating with respect to U.

When should I use U substitution versus substitution by parts?

U substitution is typically used when the integrand contains a single function that is composed of a polynomial, exponential, or trigonometric function. Substitution by parts is used when the integrand contains two functions that can be represented as a product. In general, it is up to the individual's preference and understanding of the techniques.

How do I choose the appropriate U for U substitution?

The key to choosing the appropriate U is to identify a function in the integrand that is a composite of other functions and choose that as U. It should be a function that when differentiated, the resulting expression appears elsewhere in the integrand. This will allow for the simplification of the integrand.

Can U substitution be used for definite integrals?

Yes, U substitution can be used for definite integrals. However, it is important to note that the limits of integration also need to be changed in terms of U. This can be done by substituting the original limits into the equation for U and evaluating the limits with respect to U.

Are there any drawbacks to using U substitution?

One potential drawback of U substitution is that it may not always work for every type of integrand. In some cases, it may be more time-consuming or complicated to use U substitution compared to other integration techniques. Additionally, it may be challenging to identify the appropriate U for more complex integrands.

Similar threads

Replies
12
Views
1K
Replies
1
Views
1K
Replies
11
Views
1K
Replies
7
Views
2K
Replies
5
Views
1K
Replies
12
Views
2K
Back
Top