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# Mr M's OCR (not OCR MEI) Core 4 answers June 2012 Tweet

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1. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by a10)
HOW DO YOU GET T=1 AND T=1/3

X= 2T^2 -1 Y= T^3 + T

so parrallel to y axis so x = 0?

2t^2 -1 = 0

2t^2 =1

t^2 = 1/2

t= sqrt 1/2 = root 2/2(rationalised)

thats what i got then i subbed in the value into the y equation to get y?

hw many marks would i lose but honestly someone explain hw they get t =1 and t=1/3 please
Gahhh I did exactly the same as you! The equation was y=t^3 - t and I think both of us somehow thought that the differential is 2t^2 -1 when it is obviously 3t^2 -1
2. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
Ooohhh how did I hate that exam... I just couldn't think straight though I see I got a few answers correct :3
3. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Emissionspectra)
:O I think I've dropped a max of 4 marks
Thought you get 100%?
4. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
Absolute worst case scenario is 65/72 but with various marks for doing some work but wrong answer I predict 68-70/72 or there abouts. Solid A* I reckon, very very happy, Durham here I come
5. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Tateco)
Thought you get 100%?
I thought I had, but I got the 2nd bit of question 8 wrong.
6. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by ∫f(x))
3i) Forgot to use 4x instead of x for last two terms. Would i get follow through for doing x(1+x^2) correctly?

ii) I just put 1/4, probably wont get the mark but meh

8b (i) I got t, but didnt put coordinate, how many marks will i lose?
3i) You'll get about 4 marks I expect.

ii) No mark

8b) drop 1
7. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Tateco)
Thank you very much, on question 2 I arranged it in the by parts form but integrated x/(x+2) wrong, how many marks do you think that would lose me?

And for 1ii would you get any marks at all if you started taking them away from each other? (So made the denominators the same)
2) drop 2 marks probably

1ii) get 1 mark for geting same denominators
8. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by PhysicsMan)
Thank you.

For Q2, I got:

xln(x+2) + 2ln(x+2) - (x+2) + C

Is this not right? Because I substituted boundaries into the integral in the question and then my answer- and it turned out to be correct?
Yes that's fine. I have just factorised and incorporated the 2 in the constant.
9. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by a10)
i got 3 sqrt 5 but i didnt get 2 sqrt 5 hw many marks would i lose?
probably drop 2 marks
10. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Sgt.Incontro)
Hi Mr. M,

What is your opinion on grade boundaries?

A*?
A?
B?...

etc.

Cheers.
I wouldn't like to guess - sorry!
11. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
Thanks Mr. M youre a ledge!!

for q2. i did integration by parts but got confused and used u=ln(x+2) and dv/dx= x+2
if all my working out was correct tho and i used the right formula what would i get out of 5 marks do you think? SO annoyed at myself
12. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Mr M)
3i) You'll get about 4 marks I expect.

ii) No mark

8b) drop 1
For q2, I couldn't integrate the x/1+x bit. At the end i realised a second integration may be needed, where i let u= x and dv/dx= 1+ x and i wrote that bit down but then ran out of time. How many marks do you think I have dropped?
Thanks for the help
13. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Notsocleverstudent)

For Question 2, I showed how to do integration by parts, but used completely different u and v thingys, and I've checked in the past mark scheme and it awarded 0 marks for integration by parts if wrong u and v used
For question 3, I showed both the x^4 and x^5 terms
For question 4, I seperated the variables, intergrated whatever whatever, and got c=1/2
For question 10, i, i showed the 1st part only

How many marks dropped from all of this?
no marks for question 2

question 3 - no problem showing extra terms

question 4 - you did most of the work - probably get 4 out of 6

question 10 - full marks on 1st part, no marks on the rest
14. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by a10)
HOW DO YOU GET T=1 AND T=1/3

X= 2T^2 -1 Y= T^3 + T

so parrallel to y axis so x = 0?

2t^2 -1 = 0

2t^2 =1

t^2 = 1/2

t= sqrt 1/2 = root 2/2(rationalised)

thats what i got then i subbed in the value into the y equation to get y?

hw many marks would i lose but honestly someone explain hw they get t =1 and t=1/3 please
I think if it is a line parallel to the Y axis it has an infinite gradient !!
15. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
All I day I'd been saying to myself just remember +k on any integrals. At least its a mark. Then I forgot to put it on Q2. Would that actually be a mark on C4?
16. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Doctor.)
I'm such an idiot. For question 2 I did the Product rule, but I think I did it incorrectly? Since I ended up with 0 - i was rushed for time, so didn't get a chance to check my answer.

how many marks would I get for that? :/
You should be integrating by parts - product rule is differentiation?
17. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by 19hannah94)
Why isnt the magnitude of B sqrt5? rather than 2sqrt5?
BA = BO + OA = (i - 2k) + (-3i + 6k) = -2i + 4k

Now find magnitude.
18. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by Mr M)
Mr M's OCR (not OCR MEI) Core 4 answers June 2012

1. (i) (2 marks)

(ii) (4 marks)

2. (5 marks)

3. (i) (6 marks)

(ii) (1 mark)

4. (6 marks)

5. (i) 60 degrees (2 marks)

(ii) (3 marks)

6. Show integration by substitution (7 marks)

7. (7 marks)

8. (a) -1 (4 marks)

(b) (i) (-1, 0) (3 marks)

(ii) or (3 marks)

9 (i) (5 marks)

(ii) (4 marks)

10 (i) Show (3 marks)

(ii) Show (4 marks)

(iii) 3 : 2 (3 marks)
for 10i, if I didnt show A lies on the line but showed OA was perpendicular.
How many marks would I loose for this?

10iii, I put 3/2 : 1 - does this make a difference?

Thanks.
19. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by MeatyBeast)
On question 2 I got (x+2)ln(x+2) but no + c or -x so how many marks do I lose?
On question 4 I got to the part where I got the constant c. Was the constant c=0.5?
on 9ii I gave it as decimals in my answer is that a problem
Question 2 - you may have done this quite badly so I don't really want to guess

Question 4 yes it was and that is worth 4 I expect

9ii The question asked for rational numbers so you might drop 1
20. Re: Mr M's OCR (not OCR MEI) Core 4 answers June 2012
(Original post by alc45)
I'm so annoyed, i wrote the question down wrong for number 2 and ended up integrating (x+2)lnx instead , I'm assuming that I would get 0 marks for such a question, is that normally the case for questions like this? I did the integration by parts correct and got what i thought was the correct answer to my incorrect question,
also how many marks would i lose on question 9 for only getting the magnitude of 3root5 as my other magnitude was wrong? sorry for the long question and thanks for any help
You usually only lose 1 mark for a misread but this was such a bad misread it might cost you more than this!

question 9 get one mark
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