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AQA C2 Unofficial Markscheme 24th May 2017

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Original post by Niallll99
For 6)b)I) I'm pretty sure the translation was with the vector (4/3,0) and for the last question it asked to fine k in the form (c+1)^2 therefore k=3(c+1)^(2) +1


I thought we were supposed to put (c+1)^2 in terms of k, but either way it would probably be one mark lost for being in the wrong form :smile:
Reply 21
Original post by Elclauhton
Why is the translation -4/3 and not +4/3?


It is 4/3, the mark scheme had a typo. But anyways:

Think about factorisation. Whenever you solve a quadratic, in general, the factor (ax+b) = 0.

In the case of a translation we have ax+b where a is 3, b is -4. This is like saying (3x-4) = 0

The solution must be x = 4/3 since [3(4/3)-4] = 4-4 = 0.

In other words, the translation is the opposite of the coefficient in the bracket where x = -b/a.
(edited 6 years ago)
Reply 22
Here I was patting myself on the back, aiming for a 72/75, when I just realised that I skipped #7 :bricks: What a waste!!!
Original post by Oaxfu
It is 4/3, the mark scheme had a typo. But anyways:

Think about factorisation. Whenever you solve a quadratic, in general, the factor (ax+b) = 0.

In the case of a translation we have ax+b where a is 3, b is -4. This is like saying (3x-4) = 0

The solution must be x = 4/3 since [3(4/3)-4] = 4-4 = 0.

In other words, the translation is the opposite of the coefficient in the bracket where x = -b/a.


If you translate f(x) by 4/3 for the x-coordinate, you get f(x-4/3)
Reply 24
Original post by Andrew Dainty
If you translate f(x) by 4/3 for the x-coordinate, you get f(x-4/3)


Indeed. I missed that off - formally this is a much better explanation though.
Reply 25
What does everyone think the grade boundaries will be? IMO last year was easier and it was 59 for an A, 52 for a B.
One of the lowest recent grade boundaries was 51 for an A and 46 for a B in 2012.
Reply 27
Original post by Pdddd
What does everyone think the grade boundaries will be? IMO last year was easier and it was 59 for an A, 52 for a B.
One of the lowest recent grade boundaries was 51 for an A and 46 for a B in 2012.


I would agree. Other than the least value question last year, everything was pretty straight-forward. There were a couple more places where you could slip up on this paper so I reckon this could be:

100 UMS - 71
A - 57
B - 52
C - 47
D - 42
E - 37
Reply 28
Original post by Oaxfu
I would agree. Other than the least value question last year, everything was pretty straight-forward. There were a couple more places where you could slip up on this paper so I reckon this could be:

100 UMS - 71
A - 57
B - 52
C - 47
D - 42
E - 37


I agree pretty much, think a B might be slightly lower, like 50 or 51 just because there were some tricky questions which people will have slipped up on
I think 100 UMS will be 75 as to anyone decent enough for 100 UMS full marks on this paper will be simple enough
I didn't give 48 and 312 to nearest degree. Would I lose 2 or one?
Original post by EmilySarah00
Can someone explain the series question with the sum between K and infinity being less than 2.5 to me because I got 12 but then this says 13 and I'm so confused 😂😂


The sum from k to infinity is given by 486(23)k486\left(\frac{2}{3}\right)^k (either by using a1r\frac{a}{1-r} with a=uk=162(23)ka = u_k = 162\left(\frac{2}{3}\right)^k and r=23r=\frac{2}{3}, or by using n=kun=n=1unn=1k1un\sum_{n=k}^{\infty}u_n = \sum_{n=1}^{\infty}u_n - \sum_{n=1}^{k-1}u_n.

So solving this less than 2.5 gives k > 12.997 so it must be thirteen at least.
Original post by AVishaa
For this question:
4. A geometric series has the th term .
(a) Find and . [2 marks]
.

wouldn't you use (n-1) for the power so,
u1 = 162
u2 = 108 ?


It said the power was n, they've just written the formula in a different form to throw you off
Original post by markschemes
DId anyone else do the last question like this:

6c2 + 12c + 8 = 2k

3c2 + 6c + 4 = k

3c2 + 6c + 3 = k - 1

c2 + 2c + 1 = k - 1 / 3

(c + 1)2 = k - 1 / 3

Not as fancy as OP's but still right dammit :colondollar:


That's how I did it too I'm hoping I can still pick up the 7 marks for that 😂
Thank you so so much for this Integer123! I counted up and I think I got 53/75, so not too bad although I should have easily got full marks on the last question, in addition to the translation and stretch questions. Based off the grade boundaries from last year and a couple of years before that, I'm guessing the grade boundaries might be the following:

A = 59/75 (80/100)
B = 52/75 (70/100)
C = 45/75 (60/100)
D = 38/75 (50/100)
E = 32/75 (40/100)

If that's the case, then I think I'll just get a B, probably scoring around 71 UMS. What do you guys think?
Why would they ask for (c+1)^2 in terms of k they obviously asked for k in terma of (c+1)^2 so the answer was k=3(c+1)^2 whats all this nonsense about k-1/3 or whatever
Reply 36
in terms of k means it has to be k=
Original post by Pokester
Thank you so so much for this Integer123! I counted up and I think I got 53/75, so not too bad although I should have easily got full marks on the last question, in addition to the translation and stretch questions. Based off the grade boundaries from last year and a couple of years before that, I'm guessing the grade boundaries might be the following:

A = 59/75 (80/100)
B = 52/75 (70/100)
C = 45/75 (60/100)
D = 38/75 (50/100)
E = 32/75 (40/100)

If that's the case, then I think I'll just get a B, probably scoring around 71 UMS. What do you guys think?


I think the boundaries will be slightly lower if not exactly the same as C2 2015, around 73 for 100 i'd say .
Nooo! For question 3, I put -1 instead of +1 (forgot to minus the -1 so it's +1). How many marks would I lose and I think I got the next bit right using my value. Is there error carried forward marks?
Also knew it was either 12 or 13 but had to time to think about it so I just put 12 down. What is my luck:colonhash:
Original post by Dhanuuu
in terms of k means it has to be k=


I hope this is a joke or god help u on ur results

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