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# Integration by substitution watch

Integral of 8x/(2x+1)^0.5
I know you would use u=2x+1 then differentiate it but then i dont know what to do next
2. Write the question out on your paper clearly and carfully adding all details, you can then see what and where to substitute in your u and your du
3. Are you sure you want to use u=2x+1?I don't remember off hand if that would be best. Maybe u^2=2x+1 seems more appropriate. Otherwise I think it'd leave you with either a partial fraction integration or an integration by parts. In any case, here's how you'd substitute:

so we already have our two pieces to sub in.

Here's what I was talking about. So it's clearly not the best substitution
4. Sorry i didnt mention but the question specifically says use u=2x+1 as the substitution.
5. Okie dokie. does what I've written make sense? so you're substituting x=(u-1)/2 everywhere you see an x (including the limits if it was definite). Not forgetting to change your dx to du from the substitution equation you gave me (u=2x+1).
6. (Original post by pie_monster)
Are you sure you want to use u=2x+1?I don't remember off hand if that would be best. Maybe u^2=2x+1 seems more appropriate. Otherwise I think it'd leave you with either a partial fraction integration or an integration by parts. In any case, here's how you'd substitute:

so we already have our two pieces to sub in.

Here's what I was talking about. So it's clearly not the best substitution
What's wrong with that?

easy to integrate.
7. Nice thanks! I got those answers in the end but for some reason Wolfram has a different answer.
This is what it gives
http://www.wolframalpha.com/input/?i...x/(2x%2B1)^0.5

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Updated: February 10, 2010
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