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# OCR C4 (not mei) 18th June 2013 revision Watch

1. Arrr i need 77 in both c3 and c4 to get an A overall or i can get 90 in both in hope of an a* sighhh
2. (Original post by master y)
Does anyone know how to know the value of x for which the expansion is valid. Eg. (1+4x)^(3/2)
I got x<= -1/4 but the mark scheme says (mod x )< 1/4.... HOW DOES THIS WORK? aaaaaaaarghhhhhhhh

Thanks
The binomial expansion is valid only for values:

This is because it is an infinite series and an approximation using a few terms is only valid where the later terms become less and less significant.

Then just rearrange for x
3. Wonder if anybody could explain question 4ii

http://www.ocr.org.uk/Images/79453-q...hematics-4.pdf

This is the mark scheme if anyone wants it, I couldn't understand it even after looking at it!

http://www.ocr.org.uk/Images/97265-m...ematics-4-.pdf
Wonder if anybody could explain question 4ii

http://www.ocr.org.uk/Images/79453-q...hematics-4.pdf

This is the mark scheme if anyone wants it, I couldn't understand it even after looking at it!

http://www.ocr.org.uk/Images/97265-m...ematics-4-.pdf
What you have to do is just compare like terms from each bracket. For example, comparing (1+ax) with the expansion of (1-4x)1/4
You will get ax = -x
a = -1
Do the same for b.
5. Is there another thread for this exam? this one seems kinda empty :P
6. how is everyones revision going? iv put mine at a freeze focusing on my early exams first since C4 is still a while away...
7. (Original post by a10)
how is everyones revision going? iv put mine at a freeze focusing on my early exams first since C4 is still a while away...
Same here! C4 is the least of my worries at the moment! I've got S1 and D1 on the same day! (Friday 24th May)!
8. (Original post by JASApplications)
Same here! C4 is the least of my worries at the moment! I've got S1 and D1 on the same day! (Friday 24th May)!
ohh god Iv got S1 and D2 :/ need to get on revision ASAP those permutations and combs in S1
9. Guys any idea what 90 ums is in raw marks for C3 and C4? Roughly?

This was posted from The Student Room's iPhone/iPad App
10. (Original post by SDavis123)
Guys any idea what 90 ums is in raw marks for C3 and C4? Roughly?

This was posted from The Student Room's iPhone/iPad App
90 was 63 in Jan for C3
11. (Original post by erniiee)
As above, thanks Quest!

(Original post by Quest)

(Original post by ScarlettFierce)
Haven't done C3 like most people have... But I'm doing this paper... Nervous as I need to maintain my A by receiving an average of high Bs in S1 (resitting), C3 & C4... Going to try and aim for the A* though!

Posted from TSR Mobile
Hi guys, the threads a bit dead! Just wondering if anyone can get the answer for june 2011 q7... i keep getting -1.98 when the mark scheme says to accept -1.97 ONLY!! :O
12. Can anyone help me with this partial fractions question please?

June 12, question 9i
x2 - x - 11
___________
(x+1) (x+2)2

I managed to get C = -3, A = -1 which are both right, but I keep getting the value for B wrong
13. which differentiations and integrations of trigonometry do we definitely need to know, anyone?
which differentiations and integrations of trigonometry do we definitely need to know, anyone?
i think just cos and sin... the rest are in the formula booklet..
15. (Original post by tinkerbell_xxx)
Can anyone help me with this partial fractions question please?

June 12, question 9i
x2 - x - 11
___________
(x+1) (x+2)2

I managed to get C = -3, A = -1 which are both right, but I keep getting the value for B wrong
Isn't the denominator: (x+1)(x-2)2 ?
Anyway,
x2 - x - 11
___________
(x+1) (x+2)2

A B C
= ____ + _____ + _____
x+1 (x-2) (x+2)2

x2 - x - 11 = A(x-2)2 + B(x+1)(x-2) + C(x+1)

Sub in x = - 1: -9=9A ---> A= -1
Sub in x = 2: -9=3C ------> C= -3
Compare x2 terms: 1 = A + B so B = 1 - A = 1 - (-1) ---> B=2.

(A, B and C are supposed to be on top of each of those fractions in that order btw, didn't come out very well).
16. besides ocr papers , which other exam papers for c4 would be good practice ?
17. Hey guys, C4 is in just 12 days eh. Are you guys prepared??

I'm just marking some papers now, getting good marks but a few things here and there are definitely bugging me...
18. I've had a quick search but couldn't find the C3 thread, exam is 6 days away. Can anyone link me?
19. Can someone please explain how to find a ratio of 2 vectors, i.e:

6. Relative to a fixed origin, the points A, B and C have position vectors (2i - j +6k), (5i -4j) and (7i -6j -4k) respectively.

ii) Write down the ratio AB:BC

(part i was to prove they all lie on a single straight line)

The answer is supposed to be 3:2

Thanks!
Can someone please explain how to find a ratio of 2 vectors, i.e:

6. Relative to a fixed origin, the points A, B and C have position vectors (2i - j +6k), (5i -4j) and (7i -6j -4k) respectively.

ii) Write down the ratio AB:BC

(part i was to prove they all lie on a single straight line)

The answer is supposed to be 3:2

Thanks!
Find the direction vector of AB by doing b-a, and then find the magnitude of this (add the squares of x,y,z then square root). Do the same for BC.

does this work?

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