Edexcel C4 June 2009 Thread :) Watch

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My Alt
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Going to do Jan 09 this morning ___\o/___
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Little_Jacob
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#642
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(Original post by Kaz310)
i am i am :o: :o:

lol its just the pressure is getting to me..and forget breakfast theres no time!! even tho i had time for coco pops :cool: :cool:
That's the spirit!

I had weetabix but it didn't seem to want to go down..must be exam nerves :eek:
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Sapphire Rose
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#643
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(Original post by Kaz310)
i know! argh i cant seem 2 do intergration by sub! its impossible!!
i hope they are though! c3 was realllyy easy paper!
are u stuck on any?
I was stuck cause i forgot how to integrate 1/(x +1)^2!! I am truly an idiot! I hope I don't freeze in the exam :p:

Oh and several times have I integrated instead of differentiated! I get confused a lot :sad:

I am about to do jan 09 too alt! good luck to us both :grin:

What time are you exams people? Mine is in like 3 hours! :eek:
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milan5baros
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#644
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How and why do I seperate variables someone please ?
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crouch88
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#645
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mine is in 1.5 hours
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Kaz310
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arghh can someone plz plz plz look at june 08 paper question 8b!! i cant seem to rearrange it correctly!! i always end up getting cotxdx= 2dy/(4-y^2)

whens its actually meant to be (1/cotx)dx = 2dy/(4-y^2)

thnx

correction* 7b not 8b

thnx
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Little_Jacob
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@Sapphire Rose

2pm. That hour could make all the difference. (not )
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Kaz310
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ahh i see good luck sapphire..mine is at 1..so 3 hours and a bit now!

coco pops is better...u could have got that down easily mate lolz
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Kaz310
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ah nevermind, no need to answer my question now lol i realised u have to flip everyterm to make dx go on top. then proceed as normal.
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aayman_farzand
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Exxam starts in 1.5 hours. I'm scared
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My Alt
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(Original post by Sapphire Rose)
I was stuck cause i forgot how to integrate 1/(x +1)^2!! I am truly an idiot! I hope I don't freeze in the exam :p:

Oh and several times have I integrated instead of differentiated! I get confused a lot :sad:

I am about to do jan 09 too alt! good luck to us both :grin:

What time are you exams people? Mine is in like 3 hours! :eek:
I don't start until 1:30.

(Original post by milan5baros)
How and why do I seperate variables someone please ?
The key to solving linear differential equations of the type found in C4 is to get it into the form:

f(y)\frac{dy}{dx}=g(x)

Integrating both sides with respect to x then [email protected]

\int f(y)\frac{dy}{dx}dx=\int g(x)dx \implies \int f(y) dy = \int f(x) dx

The reason you separate the variables is so that you can integrate each side with respect to each separate variable.

(Original post by Kaz310)
coco pops is better...u could have got that down easily mate lolz
I always have Weetabix before the exams, it makes me feel like I've had something good and proper to eat (wholegrain) without the monotony of toast, and the way that a fry up or egg generally doesn't help you stop feeling queasy.
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crouch88
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I'm going to guess it's going to be a very easy paper with maximum 4-5 marks worth of tricky questions, possibly a vector sum. :P just a hunch of course
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crouch88
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(Original post by aayman_farzand)
Exxam starts in 1.5 hours. I'm scared
I can't wait to get it over with dude! :|
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Kaz310
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#654
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(Original post by Sapphire Rose)
I was stuck cause i forgot how to integrate 1/(x +1)^2!! I am truly an idiot! I hope I don't freeze in the exam :p:

Oh and several times have I integrated instead of differentiated! I get confused a lot :sad:

I am about to do jan 09 too alt! good luck to us both :grin:

What time are you exams people? Mine is in like 3 hours! :eek:
dont u have to make that equation (x+1)^-2 and then intergrate using inverse chain rule?
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fn_101
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#655
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(Original post by My Alt)
I don't start until 1:30.



The key to solving linear differential equations of the type found in C4 is to get it into the form:

f(y)\frac{dy}{dx}=g(x)

Integrating both sides with respect to x then [email protected]

\int f(y)\frac{dy}{dx}dx=\int g(x)dx \implies \int f(y) dy = \int f(x) dx

The reason you separate the variables is so that you can integrate each side with respect to each separate variable.
It makes sense but I don't understand how you know what to take onto either side if it's all joined together...I keep doing it wrong...
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Stu Laverty
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Got this then S2 until 4pm tonight

Feeling good about C4 today though. Vectors are hard, but I'll save that until the end, because I can work them out with time.
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Waterstorm
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(Original post by fn_101)
It makes sense but I don't understand how you know what to take onto either side if it's all joined together...I keep doing it wrong...
You 'seperate the variables', so bring all the y's on one side, and all the x's on one side.
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Graeme1234
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i'm crapping myself, Even though I only need a C in this paper to get a B overal, i'm not sure i'll get it.
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Alpheratz
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i still cant understand differential equations
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My Alt
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(Original post by fn_101)
It makes sense but I don't understand how you know what to take onto either side if it's all joined together...I keep doing it wrong...
Generally you are dividing. Take a simple case such as \frac{dy}{dx}=xy, you can they divide to give \frac{1}{y}\frac{dy}{dx}=x which you can then integrate. Sometimes you might have: \frac{dy}{dx}=20+y where you might have to divide by the whole thing (never add or take away, you just can't really do it at C4 (unless you are rearranging into a form where you can divide, of course)) \frac{1}{20+y}\frac{dy}{dx}=1 and then integrate from there.

Sorry I cannot stick around to help more, I have to go off to school now. You can try looking in the Student Room Revision notes, or there are some Youtube tutorialsas well, I think.

Best of Luck to everyone sitting this today!
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