Edexcel C3,C4 June 2013 Thread

$\log (9x) = \log (3x \times 3)$

Try thinking of your basic log rules

Hello pls can I have ur help? From the Jan 2010 paper for C4, i don't really understand question 4f) I tried to draw the diagram (the triangle) and then did cos (43.05)*4 sqrt 26 = the line AY

But then this gave the wrong answer, but I am still not understanding why, if you could help me with that question I would be really really grateful thanks!

i cannot attach the document but a quick google search will lead to the paper and the MS!

Sorry to bother you guys! I get it now!

Alright, then.

Just to make sure, did you get t/2?

yep! you really do love maths haha

How exactly did you infer that? I suppose I do, though

you are REALLY active on the maths forums. It's great help!

Hmm, did you do the same diagram as the one in the MS?

$\cos \theta = \dfrac{AX}{AY}$

$\dfrac{19}{26} = \dfrac{4\sqrt{26}}{AY}$

Is there anything you don't understand about this?

Yes I did the exact same diagram as in the MS . So the angle I worked out to be that and then time-sed it by the 4 sqrt 26?

The mass at time t of the leaves of a certain plant varies according to the differential equation $\frac{dM}{dt} = M - M^2$

given that at time t=0 and M=0.5, find an expression for M in terms of t.


Not sure how to do this? i tried doing $\int\frac{1}{M-M^2} \ dM = \int 1\ dt$ and using partial fractions. but i didn't get it in the form they want so i'm not sure where i'm going wrong, which is $M = \frac{e^t}{1+e^t}$

Any proofs you lot recommend learning for c3 and c4?
They all seem to come up in Solomon papers but none on the edexcel papers so I'm confused as to what I should learn


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I didnt see anyone with the correct answer only a few with mistakes in.
Here is my working:

you are correct using partial fractions so you should get

(intergral) 1/M + 1/(1-M) dm =(intergral) 1 dt
ln{M} - ln{1-M} (- sign is from the -M part) = t
ln M/1-M =t (using log rules)
M/1-M)= e^t (using expotential rule)
M=e^t - Me^t (* 1-M and multiply out brackets)
M(1+e^t)=e^t (add Me^t add factorise M out L.H.S)
M= e^t/(1+e^t) (which i believe is your answer)

Sorry such rubbish work i don't know how to do all the technical signs or whatever, is there a program for this?

You will be doing the reserve paper. A delivery company 'lost' a box full of Edexcel Maths papers, so the reserves are being used for all remaining exams.

Something similar happened last year with C4. I cannot quite remember but I think C4 papers were accidently put in with papers taken earlier at some centres.

If anything I thought the reserve paper was easier.

Hope they have mercy upon us and give us a easier paper lol

You will be doing the reserve paper. A delivery company 'lost' a box full of Edexcel Maths papers, so the reserves are being used for all remaining exams.