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    qs 8)

    summation from r=1 to r=20, evaluate 1/(r+3)(r+6)

    and

    qs 15)

    Given that f(r)= 1/r(r+1), show that f(r)-f(r+1)= 2/r(r+1)(r+2)
    Hence find summation from r=5 to r=25 of 1/r(r+1)(r+2)
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    summation from r=1 to r=20, evaluate 1/(r+3)(r+6)
    \text{Express } \frac{1}{(r+3)(r+6)} \text{in terms of partial fractions then sum by the method of differences.\\

Write out the first few and last few terms so you can see the pattern and cancel the correct terms.}

    Given that f(r)= 1/r(r+1), show that f(r)-f(r+1)= 2/r(r+1)(r+2)
    Hence find summation from r=5 to r=25 of 1/r(r+1)(r+2)
    \text{You know} \frac{2}{r(r+1)(r+2)}=\frac{1}{r  (r+1)}-\frac{1}{(r+1)(r+2)} \text{so the method is similar to above, writing\\

the first few terms after 5 and the last few before 25, then cancelling and adding}.
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    I can't help noticing how few P4 [Edexcel] problems are being posted now, compared with the same period before P5.

    It's been my experience, teaching myself these 2 modules, that the big difference between them is that you can do the P4 questions, (even if you get them wrong!) whereas I found there were several topic areas in P5, where, first time through, there were quite a few questions that I simply could not do. At least half a dozen questions in each of Intrinsic Coordinates, Conics, Reduction Formulae, Integration by substitution, had me completely stumped at the first meeting, whereas even where the P4 questions are quite complicated (calculating overlapping areas in Polar Coordinates, or SoDs [Second Order Differentials] with substitutions) you can reach an answer.

    I wonder if others agree?

    Aitch
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    (Original post by Aitch)
    I can't help noticing how few P4 [Edexcel] problems are being posted now, compared with the same period before P5.

    It's been my experience, teaching myself these 2 modules, that the big difference between them is that you can do the P4 questions, (even if you get them wrong!) whereas I found there were several topic areas in P5, where, first time through, there were quite a few questions that I simply could not do. At least half a dozen questions in each of Intrinsic Coordinates, Conics, Reduction Formulae, Integration by substitution, had me completely stumped at the first meeting, whereas even where the P4 questions are quite complicated (calculating overlapping areas in Polar Coordinates, or SoDs [Second Order Differentials] with substitutions) you can reach an answer.

    I wonder if others agree?

    Aitch
    I think you certainly have a point as I think you can get more variety in the types of P5 question, whereas P4 is a little more algorithmic in nature. I think we can expect to see a few more P4/P6 threads over the weekend though (which will be good revision for me, i'm focusing on revising for the biology synoptic at the minute).
    How did you find P5?
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    (Original post by Gaz031)

    How did you find P5?
    I got quite close to finishing the paper - just ran out of time when putting the limit values into Q6, but got the integration right I think.

    I got a couple of wrong calculated answers, but no problems with the Conics, Intrinsic Coordinates, Reduction Formulae, perhaps because I'd rehearsed the topics well. I think some of the integration techniques were quite tricky, and it was more time-consuming than most other past papers.

    Aitch
 
 
 
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