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# Edexcel C2 20th May 2015 *Official Thread* watch

1. https://c4a3f001dcd45afe69d0ceec8300...%20Edexcel.pdf

2. (Original post by a.a.k)
Why not cancwl sin2x

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Because you 'lose' the solution sin2x=0

Like in x^2+x=0, you don't just cancel the x, you factorise x(x+1) and solve.
3. (Original post by a.a.k)
Why not cancwl sin2x

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Yeah did it that way, cancelled sin2x, was easier

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4. Get some sleep guys you'll need it! Good luck with the exam! Make sure you get a good breakfast xD
5. Anyone know around how many marks is 100 ums? I got 70/75 in the 2014 R paper and I'm feeling pretty proud of myself
6. (Original post by johnhick98)
can someone please explain how to distinguish wether the trapezium rule give and underestimate or everestimate
if there's missed area under the curve its underestimate and if there's extra area is over the curve its overestimate
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7. (Original post by mrnazz00923)
Attachment 403105 ah omg what do i do next? I find this topic really hard 😫
It isn't too hard once you learn how to shift the domain. Here is my full solution for Question 6b, although I haven't checked it against any mark scheme:

(Original post by mrnazz00923)
Yeah did it that way, cancelled sin2x, was easier
Be very careful when you cancel trigonometric functions as you may end up losing some of your final values.
8. (Original post by coefficient)
Because you 'lose' the solution sin2x=0

Like in x^2+x=0, you don't just cancel the x, you factorise x(x+1) and solve.
Alright thnx. It all clear now

all clear

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9. (Original post by leoben49)
Anyone know around how many marks is 100 ums? I got 70/75 in the 2014 R paper and I'm feeling pretty proud of myself
100 ums was 75/75 last year i think 70 was around 94 might be wrong though
10. (Original post by mrnazz00923)
Yeah did it that way, cancelled sin2x, was easier

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Was the answer right. I dont think ot was

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11. (Original post by TrentL)
https://c4a3f001dcd45afe69d0ceec8300...%20Edexcel.pdf

8ii
log2(x+15)-1/2log2(x)=4
log2((x+15)/sqrt(x))=4
so 2^4 = (x+15)/sqrt(x)
16 sqrt(x) = x+15

treat as a disguised quadratic where sqrt(x) = y
y^2-16y+15=0
(y-1)(y-15)=0
y=1 or 15
x = 1 or 225
12. https://c4a3f001dcd45afe69d0ceec8300...% 20Edexcel.pdf

13. (Original post by Anon_98)
What time are you all studying until?

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1 am
14. (Original post by coefficient)
8ii
log2(x+15)-1/2log2(x)=4
log2((x+15)/sqrt(x))=4
so 2^4 = (x+15)/sqrt(x)
16 sqrt(x) = x+15

treat as a disguised quadratic where sqrt(x) = y
y^2-16y+15=0
(y-1)(y-15)=0
y=1 or 15
x = 1 or 225
thank you very much most kind!
15. (Original post by SSJ100)
1 am
Okay thank you!

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16. (Original post by TrentL)
100 ums was 75/75 last year i think 70 was around 94 might be wrong though
Does that even happen??!??! I thought UMS was supposed to be higher
17. (Original post by SSJ100)
1 am
Going to sleep now

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18. (Original post by leoben49)
Does that even happen??!??! I thought UMS was supposed to be higher
Yes i have all of last years marks against the boudries and i can see clearly that 70 was infact 92 UMS and 75 was 100
19. (Original post by TrentL)
Yes i have all of last years marks against the boudries and i can see clearly that 70 was infact 92 UMS and 75 was 100
wow that's even lower than the real percentage. I'll never understand ums
20. (Original post by TrentL)
https://c4a3f001dcd45afe69d0ceec8300...%20Edexcel.pdf

i can do 9 in a sec if you want
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