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# P5 Reduction not working for me - need help! watch

1. Ok, this ones been peeing me off: (excerise 3D q 2, Heinemann)

given that I(little n) = ∫ x(lnx)^n dx,

show that I(little n) = x(lnx)^n - nI(little (n-1))

I keep getting extra bits in the equation - am doing it by parts (of course)

I split it to ∫ (lnx)^(n-1) x lnx

use (lnx)^(n-1) as 'v'

use lnx as 'du/dx' -> integrates to xlnx-x

But cant get it to work - any suggestions?
2. The question is actually

I_n = INT (lnx)^n dx

Integrate by parts with u = (lnx)^n and dv/dx = 1.
3. Thanks alot (especially for quick reply) - never thought of doing like that.
Thats what I find hard about P5 - someone shows me, and I'm like 'sure, i understand that', but wouldnt be able to come up with the same method in the exam. *sigh*
4. thats a p3 technique, its pretty much you either know it or you don't...

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Updated: June 18, 2004
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