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# AQA Core 3 - Thursday 6th June 2013 (AM) - Official Thread watch

1. (Original post by Dirtybit)
True true point taken
not sure if that will be worth 4 marks though, that's the worry.
2. (Original post by Dirtybit)
True true point taken
(Original post by ThomT94)
not sure if that will be worth 4 marks though, that's the worry.
The answer was x(ln x)^2 - 2x ln x + 2x + C
3. Who else got ln3 or ln2, not sure which, for the last answer?
4. (Original post by ThomT94)
not sure if that will be worth 4 marks though, that's the worry.
I don't think chain rule works like that for lnx
5. (Original post by A-New-Start)
The answer was x(ln x)^2 - 2x ln x + 2x + C
It's just 2 at the end
6. UNOFFICIAL MARK SCHEME HERE:

http://www.thestudentroom.co.uk/show...0#post43005930

thanks Freddy12345!
7. (Original post by air6199)
oh right, well i got that one wrong! i drew a diagram and put the rectangles on it and thought it was over estimate. never mind will probably get 1 mark for the diagram
I thought it was an over-estimate as well - I thought the mid-ordinate rule is always an over-estimate (may be wrong, but I'm sure it says this in the book somewhere). Because the strips over-lap the curve...? I could be confusing this with the trapezium rule though...
8. (Original post by ItsAnnaYay)
Came out thinking it was just about OK. Then discussed with friends and now I'm worried. Definitely got the final answers to the vase question and last integration by substitution question wrong. And there were many question where we had to draw graphs. Not sure if they were right either...

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that's how I'm feeling right now lol
9. (Original post by Anon217)
I thought it was an over-estimate as well - I thought the mid-ordinate rule is always an over-estimate (may be wrong, but I'm sure it says this in the book somewhere). Because the strips over-lap the curve...? I could be confusing this with the trapezium rule though...
exactly what i thought :/ and that's what my diagram showed :/
10. (Original post by Freddy12345)
me
Seriously chill... if we want to go to your thread we will... gawd
11. For the ordinate rule estimation question I drew out a little diagram showing the rectangles and said that it was an under-estimate... and something about how the area of the rectangles is less than the area of she shaded region due to the increasing gradient/steep slope, or something like that. I kind of just guessed... hope it's right!
12. If I got 2LN2 +2 for the last question and the answer is 2LN3/2 then how many marks would I get for the last question
13. This is why i argue its an overestimate:

http://en.wikipedia.org/wiki/File:RightRiemann.png

Similar shape of curve also,not one for using Wikipedia as truth though

But it seems so and I did read that somewhere

Maybe the question was engineered to specifically break this common knowledge though,never know with AQA :P
14. O NO! Was the draw graph question regarding to the graph that had already given us?
( I'm 100% it was, woooow i'm an idiot)
15. (Original post by KING2011BOB)
This is why i argue its an overestimate:

http://en.wikipedia.org/wiki/File:RightRiemann.png

Similar shape of curve also,not one for using Wikipedia as truth though

But it seems so and I did read that somewhere

Maybe the question was engineered to specifically break this common knowledge though,never know with AQA :P
That's not the mid-ordinate rule though.

Look at when the gradient of the line is positive, and as the curve in the question was increasing at an exponential rate (at least in the given domain), the estimation would have therefore been lower than the actual area.
16. (Original post by tiduswakka1)
I got this aswell!
That is correct. Well done.

17. anyone can scan a full detailed answer for these two please
18. For the Last question I did the working correct all the way to the end and got 2ln(3)-2lin(2)=ln(3/2) because for some reason i thought the 2 will cancel. How many marks will i lose for that?

For the Mid ordinate rule i did the working out correct but i think i got 25.7 instead of 25.6 mainly because of a calculator error, and for the second part i put that its an Under estimate with a graph which doesn't really explain it at all. How many marks will i lose for that?

And also Integrating (lnx)^2 i got x(lnx)^2-xlnx-x but i forgot about the coefficient's of xlnx and x which was 2 so how many marks do you guys think i will lose for that?
19. for the intergral of (lnx)^2 = x(lnx)^2 - the intergral of 2lnx
20. For integral of (lnx)^2 could you split that into u=(lnx)^2 and dv=1?

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