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Official Edexcel C3 Discussion Thread watch

1. I did January 2010 for my mock today and i screwed up
The paper was full of tricky questions ... wth

I'm so depressed now
2. (Original post by Arsey)
Here is the official 'Edexcel' markscheme.

All of those who were insisting that on q9. the final range was greater than or equal to 3 and not as I had just greater than 3.... should check it out.

(sorry in advance for being petty but I remember it getting a little tiresome explaining exactly why it was just >3 and some still insisted it was >=3)
where'd you explain it ?
3. Necrobump!

I'm retaking C3 and I went through my paper I got ordered back. I lost the very last mark, using this mark scheme;

http://www.scribd.com/doc/28007674/E...Marking-Scheme

Question 9 ii b)

Find fg and state its range

f(x) = e^2x + 3, xER
g(x) = ln(x-1), xER, x > 1

I got the answer which is (x-1)^2 +3 but the range I stated was wrong.

I said the range was fg(x) >= 3 (greater than or equal), which I thought was right since (x-1)^2 is always greater than or equal to zero? So why does the mark scheme state that it is ONLY greater than 3, not equal to? Can anyone help? Thanks.

If anyone was wondering, I completely balls up the x = tany question like a few people did on this topic, because I misinterpreted what they asked. But this range/domain stuff I can't seem to get my head around most of the time.
4. (Original post by Sasukekun)

f(x) = e^2x + 3, xER
g(x) = ln(x-1), xER, x > 1

I got the answer which is (x-1)^2 +3 but the range I stated was wrong.

I said the range was fg(x) >= 3 (greater than or equal), which I thought was right since (x-1)^2 is always greater than or equal to zero? So why does the mark scheme state that it is ONLY greater than 3, not equal to? Can anyone help? Thanks.

I think because in the Q it is greater than 1 then it X-1 cannot equal zero so it has to be great than and not greater than or equal to...

That amde no sense when i tried explaining it but i bolded it as well....
5. I explained in detail why it was >3 and not >=3 earlier in the thread.

The quick answer is domains in the individual functions can affect the range of a composite function.

If as in this case f and/or g do have a restricted domain it almost certainly isn't going to be as easy as sketching the graph of the composite function... you of course can but then you will need to work backwards to calculate what the domain of the overall composite function would be.
6. (Original post by FZka)
I did January 2010 for my mock today and i screwed up
The paper was full of tricky questions ... wth

I'm so depressed now
Don't worry. That paper was really hard! Don't be depressed!
7. (Original post by Popppppy)
Don't worry. That paper was really hard! Don't be depressed!
I see. Let's hope June is going to be easier.
Thanks.
8. (Original post by FZka)
I see. Let's hope June is going to be easier.
Thanks.
It better be.
9. im resitting this exam got 86 in jan ...i really want a A*...for some reason im finding this module really hard c4 is the easiest in my opinon
10. Are you insane ^

C4 is hell.
11. (Original post by Doughboy)
Are you insane ^

C4 is hell.
what spec u doing? Im doing edexcel and im getting 95% without revising for c4...c3 is bugging me im getting low 80s
12. ^ go play with your dough
13. You wanna rub my dough? Also who deleted my post :<

I'm working some differentiation problems now. My problem is utter carelessness!
14. C3 is a piece of piss now I've done C4. C4 is only really tricky with those context diff questions and possibly the odd tricky integral
15. anyone got notes and all the formulas for c3? pls do post it
solve 8cos^3 x - 6cosx - 1 =0

where x is theta and you need to find it!
18. look at the pervious part of the question.
I'm sure they've given you/ asked you to find the vale of cos (2x+x) or sin(2x+x) ... ??
19. (Original post by FZka)
look at the pervious part of the question.
I'm sure they've given you/ asked you to find the vale of cos (2x+x) or sin(2x+x) ... ??

thnx ive got it
20. (Original post by reem02)
thnx ive got it
You're welcome. Good luck.

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