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OCR C1 Thursday 7th June

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For the (x+2)^2 quadritec equation I for (x+2)^2=-6 and 1

So rejected the -6 one cause sqrt.-6 is not a real number.

Eventually getting -1 and 3 or 1 and -3.

c was -32 and k was 7.

Did people get 50 for the area? As dy/dx worked out at 5.

Reply 21

Mayson

Yes i think i agree on all accounts.

Anyone remember the transformation question.

Describe the transformation that maps y=x^3 to y= 8x^3.

I put stretch scale factor 8 in axis. But am I right in thinking that it could have also been stretch scale factor 1/2 in x axis?

Reply 22

arpeggio

I thought the exam went well although looking over this I'm suddenly very unsure of a lot of my answers - like the area one I think I left as 5 and didn't get 50? :confused:

I got k=7 and c=30something (it might have been negative; I can't remember.) For the transformation I put "Stretch by a factor of 8 in the y direction" or something like that.

Better than C2 anyway :smile:

Reply 23

rg2005

with k, was it 7 or -7, i put 7 but if the equation said -k then surely its -7 or maybe the markscheme might accept both because that was a bit of an ambigious question

Reply 24

nutcase01

can someone please tel me wat the question was where you had 2 find teh roots where -6 wasnt 1

Reply 25

arpeggio

I think that was the polynomial where you had to substitute y in for (x+2)^2 or something similar. Or that might have been C2. My brain's gone blank and refuses to remember anything now I've finished all my exams!

Reply 26

rg2005

i think it was (x+2)^4 + 5(x+2)^2 + 6 and it said let y=(x+2)^2

Reply 27

monster101

how many marks was the circle question worth - the one which included the Q on length ab equalling 4root2?

how many marks can i get from error carried forward? i made stupid mistake and ignored the square connect to the 4 so i got 2root2.

Reply 28

Mr M

Study Forum Helper

The full answers to Core 1 OCR (not OCR MEI)

Here they are folks:

1. 3x^2 + 16 x +16

2. (a) (i) graph of y = 1/x

(ii) graph of y = x^4

b) Stretch in the positive x direction scale factor 0.5

3. (i) 6 root 5
(ii) 15 root 5

4. (i) 16 - 4k^2

(ii) k or 2 or k = -2

5. (i) A = x (20 - 2x) = 20x - 2x^2

(ii) A = 50

6. x = -1 or x = -3

7. a) f'(x) = 1 - 3/x^2

b) Gradient = 20

8. (i) (x + 4)^2 -1

(ii) Vertex (-4 , -1)

(iii) x < -5 and x > -3

9. (i) Centre (3 , 0) k = 7

(ii) a = 4

Length AB = 4 root 2

(iii) y = x + 1

10. (i) x = -1/3 or x = 5

(ii) graph of y = 3x^2 - 14x - 5

(iii) c = -32

Answers to Core 2 will follow in about 30 mins.

Mr M.

Reply 29

Mayson

Greatly appreactied, but i think that in 2b stretch in y direction scale factor 8 also works.

Reply 30

rg2005

hmm not sure about number 1, i got 3x^2 + 26 x +16 and with 2 part b, cant you also stretch in the y axis

Reply 31

arpeggio

Thank you! Where did you get these from?

I can see already that I got 2b, 5(ii) and 8(ii) wrong, although I think I must get some method marks :s-smilie:

Hopefully. Are you sure about 2b?

Reply 32

monster101

rg2005

hmm not sure about number 1, i got 3x^2 + 26 x +16 and with 2 part b, cant you also stretch in the y axis

i got same as you im quite sure were right.... hopefully

Reply 33

olichemistry

was ok appart from the circle question which i just could not remember how to do, the last question was particularly easy for such a high number of marks though.

Reply 34

wazza_utd

monster101

i got same as you im quite sure were right.... hopefully

yh i think i remember getting that too, lets just hope it was a typo error :biggrin:

Reply 35

Mr M

Study Forum Helper

Sorry question 1 was

3x^2 + 26x + 16

All the others are right I believe

Yes, the stretch is the y direction scale factor 8 is fine too

Core 2 answers now going up

Mr M

Reply 36

icecreamhead

Mr M

Sorry question 1 was

3x^2 + 26x + 16

All the others are right I believe

Yes, the stretch is the y direction scale factor 8 is fine too

Core 2 answers now going up

Mr M

Anychance someone could post the actual questions as well? for C2 and C1

Cheers

Reply 37

jimmzay

I would also like the actual questions for C1, that would be really useful, so that i can try and remember what i put for different questions to see if i got it right.
I also think i made a mistake, the answer to 8. (iii) according to this was:
x < -5 and x > -3
but i wrote
-3 < x < -5
I do not know if this is an acceptable way of writing it, can someone tell me whether it is or not.
And I really could do with the questions for 1., 6., and 8.

Reply 38

Mayson

If i recall, it is not, because x cannot fulfill both those criteria at the same time, however you will only lose the final accuracy mark.

Reply 39

jimmzay

Yeh, that's what i thought may be the case, thanks, if i only lose one mark for that, then i think i have got 99%, based on those answers, although i can't remember what i answered for 1, 6 or 8 (i).