OCR MEI FP1 May 18th 2012 PRE/POST DISCUSSION!

probably lost around 3 marks overall

for the inequality, i got 4<x<=7 instead of 4<x<7

also, probably lost 2 marks on the curve sketching, got the 2 branches right but the one on the left wrong

so 69/72 probably, considering last time I did FP1 i got 71 ums i guess i did a bit better =p

Reply 101

Toothbrush

1

Original post by MrNeilPatel

I've got S1 next week, then S2 and M1, two weeks after and then on the 21st of June is C3 :smile:

Good Luck with your exams man :biggrin:

I know Neil, im in your class!

Reply 102

username537823

14

what do u generally have to get for 100 ums in this paper guys?

Reply 103

Jam'

15

Original post by sreddy17

what do u generally have to get for 100 ums in this paper guys?

Full marks (72/72)

Reply 104

Toothbrush

1

Original post by sreddy17

what do u generally have to get for 100 ums in this paper guys?

I THINK you can generally lose 2-3 marks? considering I think 59 is usually an A, 80 UMS, i think around 2-3 marks seems accurate. Having said that, it also depends on the ease of the paper, and I think alot of people found this paper straightforward ( yet I doubt an A will go over 59, maybe upto 63 AT THE MAX)

EDIT actually its probably full marks

Reply 105

skibur

12

what were the asymtotes again?

Reply 106

Deceptively

To all those of you saying the inequality was 4<x<7, I believe you're wrong, unless you're thinking of a different question?

But if you mean 3/(x+4)<1
Remember that you can't multiply by x+4 because it could be negative so some cases would flip the sign and others wouldn't, so you have to multiply by (x+4)^2 instead, then you end up with a nasty quadratic, then it helps to draw the sketch to get the correct region, and I believe the answer should be 4+/-sqrt5 or possibly -4+/-sqrt5 - I couldn't quite decide which one...

Does that sound right to anyone else, and any confirmation on whether it's -4 or +4?

EDIT: Actually yeah, definitely +4+/-sqrt5...

(edited 11 years ago)

Reply 107

Jam'

15

Original post by skibur

what were the asymtotes again?

y=0, x=-2/3, x=4, x=-3

Reply 108

Jam'

15

Original post by Deceptively

To all those of you saying the inequality was 4<x<7, I believe you're wrong, unless you're thinking of a different question?

But if you mean 3/(x+4)<1
Remember that you can't multiply by x+4 because it could be negative so some cases would flip the sign and others wouldn't, so you have to multiply by (x+4)^2 instead, then you end up with a nasty quadratic, then it helps to draw the sketch to get the correct region, and I believe the answer should be 4+/-sqrt5 or possibly -4+/-sqrt5 - I couldn't quite decide which one...

Does that sound right to anyone else, and any confirmation on whether it's -4 or +4?

EDIT: Actually yeah, definitely +4+/-sqrt5...

3(x-4)/(x-4)^2<1
3(x-4)<(x-4)^2
3(x-4)-(x-4)^2<0
(x-4)[3-(x-4)]<0
(x-4)(-x+7)<0
-(x-4)(x-7)<0

4<x<7

Your method does not work. If you raise (x-4) to the power of three, there is, again, a chance that you end up with a negative value which would (uncontrollably) flip the sign. You multiply the top and bottom of the fraction by (x-4) forcing the denominator to be of order 2 (quadratic) and consequently positive for all real values of x; therefore, you can multiply across the inequality knowing that the inequality holds true for all real values of x.

(edited 11 years ago)

Reply 109

Deceptively

Original post by Jam'

3(x-4)/(x-4)^2<1
3(x-4)<(x-4)^2
3(x-4)-(x-4)^2<0
(x-4)[3-(x-4)]<0
(x-4)(-x+7)<0
-(x-4)(x-7)<0

4<x<7

Oh my goodness you are absolutely right... genuinely feeling like the stupidest person in the world right now... Now there goes a stupid waste of marks. And public humilitation for the win. :colondollar:

Apologies to everyone who actually managed to not make the same stupid mistake as me and my friend...

Reply 110

skibur

12

Original post by Deceptively

Oh my goodness you are absolutely right... genuinely feeling like the stupidest person in the world right now... Now there goes a stupid waste of marks. And public humilitation for the win. :colondollar:

Apologies to everyone who actually managed to not make the same stupid mistake as me and my friend...

I think I know what you did, as I got the same answer as you when I first did it...

3/(x-4) >1
3 > (x-4)^2 i.e forgot to give the numerator another (x-4)?

i got the graph completely wrong, i drew in the right asymptotes and where it cuts the axis but the curves were wrong, how many marks did i lose?

i read on past papers for a similar question of 4 branches worth 4 marks, 1 mark for asymptotes, 1 mark for cut axis points and 2 marks for correct branches

does the same apply to this q?

Reply 113

XavierJameson

Original post by sgdsuy

You have to divide it by 2 because in the first part of the question it showed you what 2/(2r+1)(2r+3) was equal to in terms of partial fractions. But in the next part of the question, where you had to do the actual summation of the series, it asked you for the sum of 1/(2r+3)(2r+1) from r=1 to 30. Therefore, you have to divide the answer to the first part of the question by 2.

Okay thank you. That's really annoyed me as i thought i was getting 100%! Don't usually make silly mistakes like that :frown:

Reply 114

skibur

12

Original post by TimetoSucceed

i got the graph completely wrong, i drew in the right asymptotes and where it cuts the axis but the curves were wrong, how many marks did i lose?

i read on past papers for a similar question of 4 branches worth 4 marks, 1 mark for asymptotes, 1 mark for cut axis points and 2 marks for correct branches

does the same apply to this q?

You would have usually only dropped one, but this one had more branches than usual and was worth more marks, I would say probably one; two max.

Reply 115

MrNeilPatel

Original post by Toothbrush

I know Neil, im in your class!

I was wondering about the C5 thing aswell :P

Reply 116

TimetoSucceed

7

i was stressing so hard on question 3 so i saved it until the end, i got it wrong because i wrote a-7 and 6a/6 - 42a/6

then i realised what i did wrong, and got a sheet of paper and got the right answer.

It was very messy and i'm not sure i crossed out all the wrong working out as it was literally last minute, but i got the right values of a,p and q.

Will i lose marks for messiness and potentially not crossing out ALL the wrong working out?