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Mr M's OCR (not OCR MEI) FP1 answers June 2012

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Original post by ninuzu
Hi Mr M, thanks for these
For 9.(ii) your answer is 1/2(1, root3, -root3, 1). I halved everything and left it as a decimal so I got (0.5, 0.866, -0.866, 0.5) Would I still get the marks??

I'm trying to make the brackets look vaguely like a matrix there.
Also, for the shear question, I put a shear parallel to the x-axis scale factor 2, would that gain any marks?


Decimals in that matrix is fine.

You might drop a mark there. I haven't looked at a FP1 mark scheme for a few years so I don't know how fussy they are about language.
Original post by Mr M
Probably but not certainly.


Sorry I double posted now can't edit so ignore my other quote :tongue:
Reply 42
Thank you again for the answers, I got one half of the matrix right and one half wrong for 9) ii) ? How many marks would I lose?
(edited 11 years ago)
Original post by Ugachaka
Question 6 (ii) was (1/A - 1)(1/B - 1) where A and B are roots, i think? . I got the answer to this as 3, how did you get 8/5?


c/a from quadratic?
Original post by Mr M
Decimals in that matrix is fine.

You might drop a mark there. I haven't looked at a FP1 mark scheme for a few years so I don't know how fussy they are about language.


I also put this, they usually mention the term invariant but it means more or less the same thing :/
Reply 45
Mr M, could you post Question 6, what was the original quadrtatic?
Reply 46
Original post by Mr M
c/a from quadratic?


I think i might have overcomplicated the question, when you subsitute in the (1/u+1)? does this change the roots aswell?
yeah when you put 1/(u+1) the new roots are (1/x) -1 as that is the point of the substitution
Reply 48
for qs 6 , would you get a error carried forward for part ii?
Reply 49
Original post by As_Dust_Dances_
3/2 - 1/(n+1) - 1/(n+2) or something like that is what I got for 8ii)


This is correct and would get full marks.

Mr M is far too quick; some of us still have to teach! (A day of FP2 for me)

I can concur with all his (edited) answers. I would suspect that for Q4 n(n2+1) would get full marks, but can't guarantee it.
Reply 50
For the summation series question (first part) finding the sum to N, instead of simplifying the answer to 3/2 and the n stuff i put 1 + 1/2- 1/n+1 and the other n thing. Would i lose a mark?
Reply 51
Original post by BenjaminKyle
how many marks in total would i lose for stupidly drawing the loci |z|=|z-8| due to a misread (so that I ended up with a vertical line through (4,0) .... although i did do the circle and shade the right area of the circle correctly) - however i am worried i've made myself lose a lot of marks here as there was more than one part to the question dependent on the loci (such as the intercepts). Ahh i feel so ridiculous, this kind of problem never normally phases me, i honestly don't know what happened!


I'd imagine you would get carry on marks anyway, for drawing the wrong loci in the first place.
Reply 52
would you say this was a harder or easier than average paper? personally i thought the only tricky question was the induction Q which i could not do, but no one else seems to be fased by it.
for that induction question you have to do [SUM OF 4*3^k] + [4*3^(k+1)] since you have assume P(k) to be true you can then use it again
Reply 54
Original post by crazymanny00
for that induction question you have to do [SUM OF 4*3^k] + [4*3^(k+1)] since you have assume P(k) to be true you can then use it again


i did that but i couldn't get it into the right format. how many marks do you think i lost
Mr M,
I may have been a little bit silly and misread 6ii and thought that they were asking for (1/α -1) and (1/β -1) to be worked out separately. I worked these out to be:
-11/10 +- i root(39)/10

How many marks out of three do you think I would get?
Thanks
Reply 56
why was the rotation clockwise, because according to the formula book, its anticlockwise

Untitled.png

because when you do cos -1 (0.5) you get 60 degrees so it must be 60 degrees anticlockwise
Original post by KoalaKim
why was the rotation clockwise, because according to the formula book, its anticlockwise

Untitled.png

because when you do cos -1 (0.5) you get 60 degrees so it must be 60 degrees anticlockwise

You need to look at the sin part. -sin(60) = -0.866 when we wanted it to be positive in that position.

So the angle we are rotating anticlockwise must be -60
Hence 60 degrees clockwise
Reply 58
Original post by TehCoolNerd
You need to look at the sin part. -sin(60) = -0.866 when we wanted it to be positive in that position.

So the angle we are rotating anticlockwise must be -60
Hence 60 degrees clockwise


so why does the cos bit give you positive 60?

oh, i get it!!! how many marks will i loose???
(edited 11 years ago)
Original post by KoalaKim
why was the rotation clockwise, because according to the formula book, its anticlockwise

Untitled.png

because when you do cos -1 (0.5) you get 60 degrees so it must be 60 degrees anticlockwise


I double checked by drawing a diagram of the unit square under the transformation and it turns 60 degrees clockwise. That was also the formula I used :smile:

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