Integration by Substitution: What Went Wrong in Solving \int x(x^{2}+5)^{75} dx?

Click For Summary

Homework Help Overview

The problem involves evaluating the integral \(\int x(x^{2}+5)^{75} dx\) using integration by substitution. The original poster expresses confusion regarding their solution compared to a provided answer.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the original poster's approach and suggest differentiating the proposed answers to verify correctness. There is a mention of using substitution with \(u = x^2 + 5\) and the corresponding differential.

Discussion Status

The discussion is ongoing, with participants providing hints and checking assumptions related to the differentiation and substitution process. The original poster acknowledges a realization after receiving feedback.

Contextual Notes

There is an emphasis on the importance of correctly applying the chain rule and accounting for constants during substitution, which may have led to the original poster's confusion.

Stratosphere
Messages
373
Reaction score
0

Homework Statement


I've come across the problem
[tex]\ \int x(x^{2}+5)^{75} dx[/tex]


Homework Equations





The Attempt at a Solution


Once going through the whole problem I got [tex]\ \frac{(x^{2}+5)^{76}}{76}+c[/tex]
but the text I have said the answer was, [tex]\frac{1}{152}(x^{2}+5)^{76}+c[/tex].
What did I do wrong?
 
Physics news on Phys.org
Did you try differentiating the answers to see which one gives you [tex]x(x^{2}+5)^{75}[/tex] ? Remember to apply the chain rule and that differentiating [tex]x^{2}+5[/tex] gives 2x
 
Presumably you let u= x^2+ 5. Then du= 2x dx. You forgot the "2".
 
Oh, now I see, thanks.
 

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
Replies
7
Views
2K
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 54 ·
2
Replies
54
Views
17K
Replies
9
Views
3K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K