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# AQA Core 4 - Monday 10th June 2013 (AM) - Official Thread watch

1. (Original post by GeneralOJB)
For i, you just need to differentiate the expression at the start and replace your function of t for N.

For ii, you just need to find d/dN(dN/dt) and set it equal to zero, solve for N, then solve for t using the original equation.

Thank you
I just have a small question, what happens to the 4000N at the bottom for 7bii)?
2. Does anyone know where I could find extra questions on vectors because it is the topic I am least confident on?
3. (Original post by smarties94)
Thank you
I just have a small question, what happens to the 4000N at the bottom for 7bii)?
Once you equal dN/dt = 0

you can times both sides by 4000 which will cause the 1/4000 to disappear this is done before you differentiate again
4. I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?
5. (Original post by rwallace918)
Does anyone know where I could find extra questions on vectors because it is the topic I am least confident on?
Have you looked at the old spec papers which are basically the same? They have a number of vector questions. They can be found here.
6. PRSOM for Bord3r - why that got negged is unfathomable
7. (Original post by Jordn)
I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?
I don't think this is quite correct.

When you integrate 1/kx, where k is some constant, the reason you have to put a coefficient in front of your answer is so that, when you integrate it, it's in the form f'(x) / f(x)

for example, integrating 1/2x = integrating 1/2 * 2/2x

2/2x is of the form f'(x) / f(x) - i.e differentiate the denominator and you have the numerator

This means you can use the ln (f(x)) rule on that, so integral of 2/2x = ln 2x

1/2x = 1/2 * integral of 2/2x = 1/2 ln2x

integral of 3/x, as you say, is the same as 3 integral 1/x
so 3lnx

hope it helps
8. (Original post by Jordn)
I Have always thought intergration by inspection was

1/x = ln|x|+c so 1/2x = 2ln|2x| + c

or 3/x = 1/3ln|x| +c

but this mark scheme is telling me differently
have i been taught wrong?
You can use this as a formula that always works.

Basically whatever is on the bottom goes inside the ln and you divide by it's derivative. If there is a constant there on top it remains as it was.
9. (Original post by bugsuper)
PRSOM for Bord3r - why that got negged is unfathomable
Haha thanks but I'm not too bothered.
10. Not sure if it has been posted before, but is there anyway I could get my hands on the January 2013 Core 4 paper?

Only teachers can access it from the AQA website, and I wanted to look at it before tomorrow..
11. (Original post by FishyTim)
Not sure if it has been posted before, but is there anyway I could get my hands on the January 2013 Core 4 paper?

Only teachers can access it from the AQA website, and I wanted to look at it before tomorrow..
See page 2 of this thread, comment 23. GeneralOJB posted it.
12. (Original post by FishyTim)
Not sure if it has been posted before, but is there anyway I could get my hands on the January 2013 Core 4 paper?

Only teachers can access it from the AQA website, and I wanted to look at it before tomorrow..
The paper was just bad. It would discourage you.
13. (Original post by Bord3r)
See page 2 of this thread, comment 23. GeneralOJB posted it.
Thanks so much, (and obviously thanks to GeneralOJB as well)!
14. does anyone have any tips on forming differential equations from information given? also the grade boundaries for the last two summer c4s have been 51 and 53 which is very low, hopefully this years paper will be similar as i got an a when doing these two papers, also vectors are complete bs to me i just cant visualise them =[
15. Can someone tell me the two hardest C4 papers? I want to do them today for last minute practice!
16. (Original post by kevloui)
The paper was just bad. It would discourage you.
It was really, really bad. I just did June 07 and it was ridiculously straight forward compared to it. Anyone who says exams have got easier hasn't seen recent AQA maths papers.
17. The plus side to this is that as the papers have got steadily harder, the grade boundaries have declined.

I don't think this entirely compensates for the increased difficulty of the papers - if you literally don't know how to do a big question, you're going to have problems regardless of how low the grade boundaries are - but it's a little helpful.
18. (Original post by Enginerd.)
Can someone tell me the two hardest C4 papers? I want to do them today for last minute practice!
It's personal opinion really but I'd say Jun 12 and Jan 13, but Jun 11 could be up there too
19. (Original post by Bord3r)
It was really, really bad. I just did June 07 and it was ridiculously straight forward compared to it. Anyone who says exams have got easier hasn't seen recent AQA maths papers.
I couldn't agree more. I did jan 07 yesterday and it was nothing compared to that. I swear it was 53 for an A? If so, that says it all...
20. (Original post by The H)
It's personal opinion really but I'd say Jun 12 and Jan 13, but Jun 11 could be up there too
Yea I agree, tho june 11 weren't as bad

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