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# Review ex 2, qu 71a watch

1. This is from the heinemann P3 book

integrate x(x-1)^r with the limits 2 and 1
using a 'suitable substitution'

Eerrmm... any help greatly appreciated. I need to improve my 59/90 last time! (bizarrely, I did better in P4 with 60, despite it being a nightmare!)
2. What is r?
3. Let u = x-1, du/dx = 1

Becomes
(u-1)u^r = u^(r+1) - u^r.
4. (Original post by JamesF)
Let u = x-1, du/dx = 1

Becomes
(u-1)u^r = u^(r+1) - u^r.
is (u+1)u^r and that works out...

cheers! I started using that substitution, and then decided to try and put x's back in too early, instead of changing limits.... got messy. Thanks for sorting that though!

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Updated: June 8, 2004
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