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Edexcel FP2 Official 2016 Exam Thread - 8th June 2016

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Original post by CALI1198
Thank god. I just saw someone talking about whole numbers for that one. Would have been dreadful if i didnt even get that.

How many marks would you drop on the method of differences Q if you coikdnt get past doing the whole r=1,2..n stuff?


Out of 5, maybe 3? Worst case scenario would be 4.

@Zacken might know. (Sorry for bothering you bud :biggrin:)
Original post by Insight314
Told you m8. Doubting my maths skills. Now I can finally act like a proper lad and tell my friends it is a very easy paper.

Btw, is Student's method wrong then? It was posted a few pages back but he pretty much did the same think except differentiating the ODE at the start so he can get a 2nd order ODE. This makes him get a quadratic auxiliary equation, with roots 0 and -2, whereas my method only has one root which is -2. So his complementary function would be wrong.




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No it is not wrong because you later show the constant corresponding to it is 0...
Original post by Insight314
Posted above m8.

How did you find it?

I bet the mandem down at STEP prep thread finished this paper in half the time.


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Lol, I found it quite tough. I get overly nervous during exams.

I finished in less than an hour, but then realised I had done it all wrong, so had to do it all again.

I might lose one or two marks, because I seem to have missed evaluating for the constant of integration for the p, q, r one. Did the p, q, r one in two ways too.
Original post by CALI1198
Thank god. I just saw someone talking about whole numbers for that one. Would have been dreadful if i didnt even get that.

How many marks would you drop on the method of differences Q if you coikdnt get past doing the whole r=1,2..n stuff?


Yeah, drop 3 or 4.
That's cool. I was thinking 4 as I didn't even spot to split it up. Ah well, hopefully M2 and FP3 are kind if I have any chance of uni still

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Original post by Student403
No it is not wrong because you later show the constant corresponding to it is 0...


prsom
Original post by Insight314
Told you m8. Doubting my maths skills. Now I can finally act like a proper lad and tell my friends it is a very easy paper.

Btw, is Student's method wrong then? It was posted a few pages back but he pretty much did the same think except differentiating the ODE at the start so he can get a 2nd order ODE. This makes him get a quadratic auxiliary equation, with roots 0 and -2, whereas my method only has one root which is -2. So his complementary function would be wrong.




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No it ain't wrong cause if y satisfies the first one then it satisfies the second order thing but he found the zero part so it was all good.


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Original post by Student403
No it is not wrong because you later show the constant corresponding to it is 0...


Yeah I thought it was equivalent but isn't your c.f. y=A+Be2θy = A + B e^{-2\theta} ?


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Original post by EricPiphany
Lol, I found it quite tough. I get overly nervous during exams.

I finished in less than an hour, but then realised I had done it all wrong, so had to do it all again.

I might lose one or two marks, because I seem to have missed evaluating for the constant of integration for the p, q, r one. Did the p, q, r one in two ways too.


Yeah, I guess it was a bit too fiddly, especially at the end. You really shouldn't worry about it tbh, especially since you are such a god in STEP you would probably get in Cambridge even if you flop your other FM modules. :biggrin:


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4(b)?

Unsure if the solution is missing + (c/5), or if there was additional info bar the initial FOD equation
Original post by Fbiemad
I got the same as you. Is that correct?



As far as I am aware; that is my worked solution
Original post by Insight314
Yeah I thought it was equivalent but isn't your c.f. y=A+Be2θy = A + B e^{-2\theta} ?


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CF is in the form (A + Btheta)e-2theta. It is later shown that B = 0 and A = 1/5. Also the PI is shown to be 2/5 sintheta - 1/5 costheta
That second order de was like y = Ax^2 + Bx - (1/12)x^-2 wasnt it.
Original post by Craig1998
That second order de was like y = Ax^2 + Bx - (1/12)x^-2 wasnt it.


Correct.
Original post by Student403
CF is in the form (A + Btheta)e-2theta. It is later shown that B = 0 and A = 1/5. Also the PI is shown to be 2/5 sintheta - 1/5 costheta


All right. Sorry then. :biggrin:


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Original post by Student_2357
To be honest, apart from Q4, they were all standard questions. There were two obvious ways to approach 4b, one was treating it as a 1st order differential and finding the integrating factor etc. and the second method was differentiating it again and treating it as a 2nd order then solve. A*-70?


Final Q was nastier than normal and a hard Q throws people so they do worse throughout.
can anybody attach the model answers?
Anyone got the paper? I mean I doubt it, dunno why I ask, but whatever, interested to see it
For question 2, how many marks for 2b) worth? I didn't get a=-3 and b=9 I got b as -4 because I didn't think to use what we learned in FP1 and just subbed in 1, 2, 3... n-2, n-1 and n and noticed that you had multiple (n-2) terms so did (n/2)(n-2) for some reason. Any idea how many marks I will have lost? I got a=-3 though...
Original post by Insight314
Huh?

Which method?

1. Double IBP
2. Treating it as 1st order ODE and using auxiliary equation, like in M5 Chapter 1.
3. Exponential form of sin, which Mathemagician suggested.



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if you used the exponential form wont your answer be left imaginary?

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