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# FP2 doubt watch

1. In the Edexcel book, on page 15 ( the answer to Example 4 , part b ) why is it written as 1/2 + 1/3 instead of the general terms 1/(n-1) and 1/n ?

thanks for any help!
2. bump
3. bump
4. How about writing out the problem so that the large amount of people here without that textbook know what your question is?
5. Example 4

a. Express 2/(r+1)(r+3) in partial fractions
b. Hence prove by method of differences that

n
Sigma 2/(r+1)(r+3) = n(an+b)/6(n+2)(n+3)
r=1
6. I don't know the method of differences so I can't really help you on part (b). If the answer has no 's in it, I assume it's because they will all cancel out or something.
7. Method of differences = Telescoping.
(Original post by princejan7)
In the Edexcel book, on page 15 ( the answer to Example 4 , part b ) why is it written as 1/2 + 1/3 instead of the general terms 1/(n-1) and 1/n ?
I'm not sure what you mean. The question looks OK to me. Start by writing:

then try telescoping it.
8. (Original post by Piecewise)
Method of differences = Telescoping.
I'm not sure what you mean. The question looks OK to me. Start by writing:

then try telescoping it.
Im assuming you have the book with you...

At part b after using method of differences up till r = 3, a (1/2), (1/3), - (1/n+2) and
-(1/n+3) are left over.
Why isn't the (1/2) and (1/3) written as (1/n-1) and (1/n)?

Thanks!

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Updated: March 26, 2011
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