OCR (Not MEI) C2 January 2013 Discussion

How on earth do you work out the value of x in question 6? I applied the formula u_n= a + (n-1)d to the terms 2x and the second one. Then I did the same for the third and second terms; and could not get any further.

Also, question 9, when integrating, how on earth did they get a cubic value?

I've looked through the past papers, and there's surely not a difficult paper like today compared to the others. :s-smilie:

for no. 9 when you intergrate and everything you get something like:
aX^2 + bX + c/x = 0
It was important to spot that it equalled to 0, because this mean you could multiply both sides by 'X' hence giving a cubic :smile:

I just about managed to spot it myself :redface:

Reply 101

mcfc@2012

And it definitely said a was positive? Damn it!

Reply 102

stirkee

19

Original post by mossss

anyone remember any of the questions?

I'll post what I remember (for definite)

4i) Expand (2 + x)⁵

ii) Hence find the coefficient of y³ in the expansion of (2 + 3y + y²)⁵? (something along the lines of) A horizontal line is drawn through the curves y=log₂x and y=log₂(x-3). It crosses y=log₂x at P and y=log₂(x-3) at Q. The x coordinates of P and Q is the same, c, and the distance PQ is 4. Find c.

(edited 11 years ago)

Reply 103

KRJACK

What did anyone get for the value of k?

Reply 104

abzy1234

OP

14

Original post by BawanHama

for no. 9 when you intergrate and everything you get something like:
aX^2 + bX + c/x = 0
It was important to spot that it equalled to 0, because this mean you could multiply both sides by 'X' hence giving a cubic :smile:

I just about managed to spot it myself :redface:

Ahh I get it now! Thanks! So so so subtle. I bet these examiners can see through ice :tongue:

Reply 105

stirkee

19

Original post by BawanHama

for no. 9 when you intergrate and everything you get something like:
aX^2 + bX + c/x = 0
It was important to spot that it equalled to 0, because this mean you could multiply both sides by 'X' hence giving a cubic :smile:

I just about managed to spot it myself :redface:

Correct. You ended up with something along the lines of 3x²+ ax + 8/2x = 0 I think, and so you could multiply everything by x to get the cubic!

And if anyone is confused, the question used a's whereas I just used x's if that reminds you of which one it was! :biggrin:

Reply 106

stirkee

19

Original post by Luppy021

Cant have the log of a negative number, I got 3.2

I got 3.2 as well :smile:

.

Reply 107

olivers16

Original post by KRJACK

What did anyone get for the value of k?

9 over 10 but I'm pretty sure im wrong

Reply 108

KRJACK

Original post by olivers16

9 over 10 but I'm pretty sure im wrong

not to be mean but i really hope you're wrong i didn't get that :frown:

Reply 109

FootInMouth

If u all want the answers then contribute Qs if you can remember them and Mr M will post the answers

Reply 110

stirkee

19

Original post by FootInMouth

If u all want the answers then contribute Qs if you can remember them and Mr M will post the answers

Is there any way to tag a member?

Here's what I remember for sure:

4i) Expand (2 + x)⁵

ii) Hence find the coefficient of y³ in the expansion of (2 + 3y + y²)⁵? (something along the lines of) A horizontal line is drawn through the curves y=log₂x and y=log₂(x-3). It crosses y=log₂x at P and y=log₂(x-3) at Q. The x coordinates of P and Q is the same, c, and the distance PQ is 4. Find c.

(edited 11 years ago)

Reply 111

Ranibizumab

9

Original post by stirkee

Is there any way to tag a member?

Here's what I remember for sure:

4i) Expand (2 + x)⁵

ii) Hence find the coefficient of y³ in the expansion of (2 + 3y + y²)⁵? (something along the lines of) A horizontal line is drawn through the curves y=log₂x and y=log₂(x-3). It crosses y=log₂x at P and y=log₂(x-3) at Q. The x coordinates of P and Q is the same, c, and the distance PQ is 4. Find c.

There was a question asking what transformation maps log₂x onto log₂(x-3)

log₂x has co-ordinates (a , something). Find a.

log₂(x-3) has co-ordinates (something, b) Find b.

Reply 112

saberahmed786

13

Original post by FootInMouth

If nobody has the paper we need to try and create a copy of the questions

The question with the tangents i remember it:

I'll draw a diagram on fireworks and upload it for you all :smile:

the question was (not exactly worded correctly but I these were the questions with the allocated marks):

5) The radius of two circle (from points A and B) have a radius of 7 cm. The radi meet at point C. The distance between A and B is 12 cm.

i) Show that the angle CAB is 0.5411 radians (2 marks)
ii) find the perimeter of the shaded region (2 marks)
iii) find the area of the shaded region (5 marks)

Reply 113

stirkee

19

Original post by saberahmed786

The question with the tangents i remember it:

I'll draw a diagram on fireworks and upload it for you all :smile:

the question was (not exactly worded correctly but I these were the questions with the allocated marks):

5) The radius of two circle (from points A and B) have a radius of 7 cm. The radi meet at point C. The distance between A and B is 12 cm.

i) Show that the angle CAB is 0.5411 radians (2 marks)
ii) find the perimeter of the shaded region (2 marks)
iii) find the area of the shaded region (5 marks)

Yeah that's right, well remembered :biggrin:

Reply 114

stirkee

19

Original post by Ranibizumab

There was a question asking what transformation maps log₂x onto log₂(x-3)

log₂x has co-ordinates (a , something). Find a.

log₂(x-3) has co-ordinates (something, b) Find b.

Ah yeah of course. Can you remember which Q this was?

Something is telling me it was Q6 but I'm not sure.

Reply 115

olivers16

I think the last question started with the 2a and a with 2x^.......5x^3+4 all over x^2 and you were asked to make it show t = .......+2, sorry, all I remember, hopefully someone can fill in the blanks.

Reply 116

KRJACK

There was one something like, log2a=3 find value of a

Reply 117

stirkee

19

one of the guys in my fmaths class missed out 4 questions entirely on the paper :s-smilie:

Feel bad for him :frown:

Reply 118

username1102419

I was really confident before this exam and now I feel awful, but here's what I remember from it

I can't remember all, but..

Q.4 I think was the binomal expansion but I'm not sure..
Q.6 was the whole u1=2x, u2=x+4, u3=2x-7
Q.7 was the cirlcles and shaded area question
Q.8 was the logs (remember the log graph on the back page?)
Q.9 was the integrating between 2a and a

here's to an easier re-sit in june :frown:

Reply 119

Lard