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OCR (not MEI) C2 - Wednesday 20th May 2015

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username1533709

Q8(i)
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/Specimen%20QP%20-%20C2%20OCR.pdf
Im stuck .Will this part involve logs ?

Original post by giantbecky

the answers are 3 and 1/2 and actually I just tried 1/2 and I don't think that works as -7x1/2 +3 = -1/2 and you can't take logs of negative numbers...

So maybe the textbook is wrong? :s-smilie:

:s-smilie:

Yeah the textbook is wrong, and the correct answers are:
(−7±√73)/4

Original post by Sahil_

Yeah the textbook is wrong, and the correct answers are:
(−7±√73)/4

okay thankyou!!

Original post by Kadak

Q8(i)
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/Specimen%20QP%20-%20C2%20OCR.pdf
Im stuck .Will this part involve logs ?

Yep. 2=1.25^x

log1.25(2)=x
therefore x=3.11

*uses a^b=c is the same as loga(c)=b

username1533709

Original post by Issy :)

Yep. 2=1.25^x

log1.25(2)=x
therefore x=3.11

*uses a^b=c is the same as loga(c)=b

Im confused on the mark scheme for part ii of the question.They used 1.25^0 but I only used from 1.25^1 to 1.25^4.Why am I wrong ?

Checking in :colonhash:

:colonhash:

How's everybody doing? :smile:

:smile:

Because the limits are 0 and 4 because it is bound by the y-axis where x=0 :smile:

:smile:

therefore 1.25^0 not 1.25^1 . Hope this helps

Original post by Kadak

Im confused on the mark scheme for part ii of the question.They used 1.25^0 but I only used from 1.25^1 to 1.25^4.Why am I wrong ?

username1533709

Original post by Issy :)

Because the limits are 0 and 4 because it is bound by the y-axis where x=0 :smile:

:smile:

therefore 1.25^0 not 1.25^1 . Hope this helps

Ok,part (iii),I said it was an underestimate because it looks like its under the curve,but the mark scheme says its an overestimate.Like wtf ?

Original post by Kadak

Ok,part (iii),I said it was an underestimate because it looks like its under the curve,but the mark scheme says its an overestimate.Like wtf ?

The tops of the trapezia are above the curve- see pic below :smile:

:smile:

maths 2.png

username1533709

Original post by Issy :)

The tops of the trapezia are above the curve- see pic below :smile:

:smile:

maths 2.png

Thank you so much !I just realsied when I make the trapezia,the line will go above the curve.Ty.

username1533709

Original post by Issy :)

The tops of the trapezia are above the curve- see pic below :smile:

:smile:

maths 2.png

Sorry again,but Im stuck on q9 part i.
I have twwo factors with an unkown remainder, and having the a there throws me off.

F(2)= F(-2)
therefore (imput this value for x)...
4a+2b+2= 4a-2b-14
4b=16
b=4
then work out a. Basically the a cancels but you need to be brave and work through the calc that looks too complicated to do. Sneaky exam board. :wink:

:wink:

Original post by Kadak

Sorry again,but Im stuck on q9 part i.
I have twwo factors with an unkown remainder, and having the a there throws me off.

username1533709

Original post by Issy :)

F(2)= F(-2)
therefore (imput this value for x)...
4a+2b+2= 4a-2b-14
4b=16
b=4
then work out a. Basically the a cancels but you need to be brave and work through the calc that looks too complicated to do. Sneaky exam board. :wink:

:wink:

Ty once again !
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/June%202011%20QP%20-%20C2%20OCR.pdf
From question 8(ii) to 9v0,Im stuck.Can you guide me please ?

Original post by Kadak

Ty once again !
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/June%202011%20QP%20-%20C2%20OCR.pdf
From question 8(ii) to 9v0,Im stuck.Can you guide me please ?

8ii) 2^x - 3
2^0 - 3
1 - 3 = -2

8iii) 0 = log2^x - 3
3 = log2^x
x = log(base2)3

I think of it as 2 to the power of x = 3 and the power always goes to the right. The thing that is getting 'the power' is the base.

iv) y = 2^p - 3 (p,62)
62 = 2^p - 3
65 = 2^p
log65 = log2^p
log65 = plog2
p = log65/log2

Trapezium rule is easy.

Original post by Kadak

Ty once again !
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/June%202011%20QP%20-%20C2%20OCR.pdf
From question 8(ii) to 9v0,Im stuck.Can you guide me please ?

Quick question, during the trapezium rule, is it the odd numbers multiplied by 2 ?

Original post by Kadak

Ty once again !
https://68baf9f6baae001b7abe18b6e880c559742888e3.googledrive.com/host/0B1ZiqBksUHNYUlVQUzA0enkzVFU/June%202011%20QP%20-%20C2%20OCR.pdf
From question 8(ii) to 9v0,Im stuck.Can you guide me please ?

Original post by ADotCross

Quick question, during the trapezium rule, is it the odd numbers multiplied by 2 ?

No it's all except the first and last :smile:

:smile:

the formula is on the data sheet :smile:

:smile:

Original post by giantbecky

No it's all except the first and last :smile:

:smile:

the formula is on the data sheet :smile:

:smile:

Just realised that I'm thinking about core 3' thanks

username1533709

Original post by Issy :)

Posted from TSR Mobile

I'm confused.For the trapezium rule,I thought it would be this set up,

1432059985914.jpg27.6KB

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