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# Edexcel P2 After-test Discusion watch

1. (Original post by !Laxy!)
Yay! It was soooooooooo easy!

From the answers on here i've got 72 out of 75. I dropped 2 marks on the amount of water going past the river thingy. and one mark on the first part of the trig as i got 1/3rt3 but no -ve sign.

I reckon grade boundary for an A will be about 66/75 what do others think??
the trig answer was definately -ve.

About grade boundries: the overall grade at the end is not based only on P2 result, so how the hell can you say that the grade boundry will be anything like 66/75?? Based on the P1 paper it's likely to be about 73/75! And on P3 probably 60/75...66/75 is meaningless.
2. (Original post by !Laxy!)
I thought f(x) was 2/x-1 so inverse was: (2/x) +1 If i remember correctly?
f^(-1)(x)=(2/x)+1=(2+x)/(x) is what I got.
3. (Original post by CrazyChemist)
the trig answer was definately -ve.

About grade boundries: the overall grade at the end is not based only on P2 result, so how the hell can you say that the grade boundry will be anything like 66/75?? Based on the P1 paper it's likely to be about 73/75! And on P3 probably 60/75...66/75 is meaningless.
Yes it is. each exam has different grade boundries. Any P2 likley to be about 61 id say. maybe a little more.
4. (Original post by CrazyChemist)
the trig answer was definately -ve.

About grade boundries: the overall grade at the end is not based only on P2 result, so how the hell can you say that the grade boundry will be anything like 66/75?? Based on the P1 paper it's likely to be about 73/75! And on P3 probably 60/75...66/75 is meaningless.
It is based only on the P2 paper

Todays was very similar to June 2003 which was 66/75 for an A
5. (Original post by chats)
oh yeh sorry f(x) was 2/x-1
right:

f(x) = 2/(x-1) so just switch f(x) for y:

y = 2/(x-1)
x-1 = 2/y
x = 1+ 2/y

f-1 = 1 + 2/x

What was g(x)?
6. (Original post by chats)
It is based only on the P2 paper

Todays was very similar to June 2003 which was 66/75 for an A
Eh? How is it based only on the P2 paper? you get a grade for maths, not one for each paper...
7. y = 2/x-1
y(x-1) = 2
yx - y = 2
xy = 2 + y
x = (2+y)/y
inverse = (2+x)/x
8. (Original post by CrazyChemist)
Eh? How is it based only on the P2 paper? you get a grade for maths, not one for each paper...
Ye but each paper is scaled. I.e. P2 might be 61 to get 80UMS.
U need 480UMS in total for an A. Based on the UMS scaling.
9. (Original post by Syncman)
Ye but each paper is scaled. I.e. P2 might be 61 to get 80UMS.
U need 480UMS in total for an A. Based on the UMS scaling.
Each paper is scaled individually? I thought your marks were just added up at the end and scaled up or down.
10. (Original post by CrazyChemist)
right:

f(x) = 2/(x-1) so just switch f(x) for y:

y = 2/(x-1)
x-1 = 2/y
x = 1+ 2/y

f-1 = 1 + 2/x

What was g(x)?
g(x) was x² + 5
11. (Original post by CrazyChemist)
Each paper is scaled individually? I thought your marks were just added up at the end and scaled up or down.
Nope each paper is scaled individually.

http://www.edexcel.org.uk/VirtualCon...ort_Jan_05.pdf

See page 36 of 38. For which unit is which, see contents.
12. (Original post by josklkr)
g(x) was x² + 5
you want fg(1/4) yes?

g(1/4) = (1/4)² +5
= 1/16 +5
= 81/16

fg(1/4) = f(81/16)
= 2/(81/16 - 1)
= 2/(65/16)
= 32/65
13. (Original post by Syncman)
Nope each paper is scaled individually.

http://www.edexcel.org.uk/VirtualCon...ort_Jan_05.pdf

See page 36 of 38. For which unit is which, see contents.
Ah right - thanks
14. (Original post by CrazyChemist)
you want fg(1/4) yes?

g(1/4) = (1/4)² +5
= 1/16 +5
= 81/16

fg(1/4) = f(81/16)
= 2/(81/16 - 1)
= 2/(65/16)
= 32/65
was the question fg(1/4) or fg(x)=1/4 ???
15. (Original post by CrazyChemist)
you want fg(1/4) yes?

g(1/4) = (1/4)² +5
= 1/16 +5
= 81/16

fg(1/4) = f(81/16)
= 2/(81/16 - 1)
= 2/(65/16)
= 32/65
nah the question was fg(x) = ¼
16. (Original post by josklkr)
nah the question was fg(x) = ¼
oh damn - are you sure? That means x=2 or x =-2 yes (after quick calculation)?
17. yeh, but x>1 though i think
18. (Original post by sequence123)
yeh, but x>1 though i think
no thats only with the function f
in the function g, x is any real number
if you place any number into g you will get a positive number (because of x²) and it will be larger than 1 because of the + 5
therefore any number you place into f will be larger than one
therefore you can have -2
19. (Original post by !Laxy!)
Yay! It was soooooooooo easy!
I reckon grade boundary for an A will be about 66/75 what do others think??

I hope that for an A, it will be 75/75, but that wont bother you as it was easy
20. I thought it was a relatively easy paper, because I hammered into revision after doing badly in January. Hopefully, I'm not delusional and I have done well. One question... in the volume of a revolution questions, I changed 2ln3 to ln9... or whatever the hell ln whatever the hell, I just raised it to the power, that is ok right?

EDIT: I'm a ******, I've typed it the wrong way round.

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