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Mr M's OCR (not OCR MEI) Core 2 Answers May 2016

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Original post by ComputeiT
Using previous part:
x^2/(x+4) = 3^2 = 9
x^2=9(x+4)
x^2=9x+36
x^2-9x-36=0
(x-12)(x+3)=0
x=12 or -3

But log base 3 (-3) is undefined.
Therefore x = 12


I originally thought this and put down my answer as x = 12. But then I realised that 2log3(-3) is the same as log3(9) [(-3)^2]. So isn't -3 allowed? If you do this on your calculator you get the correct answer. I'm not saying you're wrong I just don't understand why -3 isn't allowed.
Original post by mrbeady9
I originally thought this and put down my answer as x = 12. But then I realised that 2log3(-3) is the same as log3(9) [(-3)^2]. So isn't -3 allowed? If you do this on your calculator you get the correct answer. I'm not saying you're wrong I just don't understand why -3 isn't allowed.


Sketch a graph of log3(X)
Original post by Mr M
∑n=1∞Wn=1200\displaystyle \sum_{n=1}^{\infty} W_n = 1200

N2(2a+(N−1)d)>1200\displaystyle \frac{N}{2}(2a+(N-1)d)>1200

Let a = 5 and d = 1.5 and solve.


I used both as the sum of the geometric series due to the previous question, will I get any marks do you think? I used the correct method throughout but didn't get a quadratic equation. I think I've averaged out at about 55 marks, should that be at least a C, I did want at least a B though.

Thank you for your time.
Original post by ArranJones
I used both as the sum of the geometric series due to the previous question, will I get any marks do you think? I used the correct method throughout but didn't get a quadratic equation. I think I've averaged out at about 55 marks, should that be at least a C, I did want at least a B though.

Thank you for your time.


If you found the sum to infinity was 1200, you'll get 1 mark. I doubt whether you'll get more credit as you completely misunderstood what you were expected to do.
Original post by Mr M
If you found the sum to infinity was 1200, you'll get 1 mark. I doubt whether you'll get more credit as you completely misunderstood what you were expected to do.


Okay then, thank you. I do understand the question. Just didn't do it properly in the exam, worst feeling ever!
Original post by ArranJones
Okay then, thank you. I do understand the question. Just didn't do it properly in the exam, worst feeling ever!


It's one question out of 6 modules. It won't prevent you from getting the grade you need in the end.
What was the question for 8iv?
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Ozil5
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if there a stats thread?

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