x Turn on thread page Beta
 You are Here: Home >< Maths

(C4 Integration) Quick question - Am I being stupid? watch

1. Been resolved, thanks!
2. ...

(because we can say:

3. It's rather torturous to read.

When you say U and U^(-1) cancel out, they in fact multiply to give 1.

So your integral becomes 1 + U^(-1)
4. (Original post by The0neAnd0nly)
Hi there, I am having a little problem with this question, I know the answer is:
ln(x-1)+x+c

But I cannot get to it.

This is the question:

Integrate this: ∫xx1dx

This is what I did:

So let u = x-1
therefore x = u+1, and du=dx

So
(u+1)(u^-1) du

the U and U^-1 cancel out, so leaves

∫u^-1 du, which intergrates to lnu, which is ln(x-1).

Where does the +x come from!?!?!

Sorry for the poor layout and thanks in advance!

x
x
First of all, you wrote the question slightly wrong. You mean integral of x((x-1)^(-1)) right?

The problem is, I don't see how you cancelled (u+1)/u to become 1/u.....
5. your method gives the integrand as:
6. (Original post by ghostwalker)

When you say U and U^(-1) cancel out, they in fact multiply to give 1.

So your integral becomes 1 + U^(-1)

Thank you, this is the answer I was looking for, For some reason the text came out all wrong...

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 2, 2013
Today on TSR

Did he block me?

What should I do?

Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants