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Mr M's OCR (not OCR MEI) Core 1 Answers May 2013

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Original post by Dugald
I didn't put question 8 in integer form.

On question 10 I got that k=-5 but when putting k back into the original equation and differentiating it I got dy/dx=-3x^2-6x+4-k to be dy/dx=-3x^2-6x+4-5 instead of dy/dx=-3x^2-6x+4-(-5) so got dy/dx=-3x^2-6x-1.

I carried this error forwards into the last part of the question and did dy/dx=9, then put it into quadratic form but it had no real roots. I couldn't work out where I went wrong so in the last few minutes i just went with it and proved that it had no real roots which I knew was wrong.

How many marks will I lose in total?


8) drop 1

10)i) drop 1

10iii) drop 2
Original post by Mr M
x.


Hey Mr M, thank you so much. How many marks would I lost if:

for 5i) sketch I labelled -2 and 2 on the x-axis but still got the actual sketch of the curves correct?

for 7ii) I somehow missed off the 0 and put x<5?
I'm off for a bit folks as I have work to do. Back later. Don't private message me please - ask questions here.
Reply 183
Mr M, what was question 8?
Thanks
Reply 184
Would someone mind posting the working out for the last part of the last question, I cant get my ead around it, thank you.
Original post by Mr M
That's ok then! I'll post C2 answers on Friday afternoon.


Mr M, for the last question for the stationary points i differentiated, equaled it to 0 as the gradient=0, but somehow got k= -4 instead of -5. How many marks would I lose for the answer?

Also for the final part to the last question, i stupidly did -18-9=-9:frown:. This means I got the co-ordinates as (-2,-9). However I factorised correctly and got the correct co-ordinate for x, how many marks would I lose for that? Thanks!
Original post by AspiringDoctor
Hey Mr M, thank you so much. How many marks would I lost if:

for 5i) sketch I labelled -2 and 2 on the x-axis but still got the actual sketch of the curves correct?

for 7ii) I somehow missed off the 0 and put x<5?


The curve doesn't touch the x axis so I'm not sure why you labelled anything there?

7ii) drop 3 marks
For Q7 part 2 I missed the 0 boundary, would I only lose 1 mark for this?
Reply 188
Hello Mr M,

Thanks for your answers.

1.For Question 5(iii), I put, A stretch parallel to the Y-axis by a scale factor of 2. I thought it was going from 1/x^2 to 2/x^2, thats why I did that. Will I get any marks?

Also, for Question 6, I completed the square, but got (x-0)+(y-4)=40 , and for my Centre I put (0,4) and Radius Sqrt(40).
Because this part of the question was wrong, the Point B on 6(ii) was different too, but the write answer using (0,4)

Thanks,
C94
Reply 189
Original post by Mr M
Yes.


Yay thank you! And also thanks for the answers.


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Reply 190
Original post by Mr M
I think you will lose 2 accuracy marks.


Thank you!! If this is true you have made me feel so much better!!! And thank you for the answers as well :smile:
Original post by Mr M
C2, C3, C4, FP1, FP2, M1, M2. These are the ones I teach.


Ahh, not S1? S1 will be a killer this year. It's the only Maths exam (from C1-4, FP1, M1, M2, S1) I'm underprepared for, and the papers have gotten more and more difficult every series since June 2011 (which itself was trickier than ever before). I have a feeling they will culminate this year in a "big bang". And the 100 UMS boundary will be 60. Which isn't good ...
Suppose I put two answers down with all workings, one is incorrect and one is right. How marks will i lose? ...This is for the last question
Cheers for the answers :biggrin:

Now if only I could remember what my answers were :facepalm2:
Reply 194
I put +/- 1/2 as a route instead of just as 1/2 will I still get the mark?
also think did the correct method but the wrong answer for part (iii) on the last question will I still get method marks? And if so how many?
Hey Mr M i compeleted the square for 7(ii) and wrote x= 5/2 +/- root 50/8 would i lose all marks
Reply 196
Hi I put down (0,-9) and (-2,-27) for the last question but stated A as being (0,-9) cos I thought that fit the equation given. Any ideas how many marks I'll lose?
Can't remember if for Q4 ii) it asked to differentiate to find the minimum point? I just used the values I got from completing the square...
Mr M what if I wrote question 3 out like 36X^-4??
Original post by Mr M
Mr M's OCR (not OCR MEI) Core 1 Answers May 2013


1. (i) 12512 \sqrt 5 (2 marks)

(ii) 454 \sqrt 5 (1 mark)

(iii) 555 \sqrt 5 (1 mark)


2. x=12x=\frac{1}{2} or x=1x=-1 (5 marks)


3. (i) f(x)=212x3f'(x)=2-\frac{12}{x^3} (3 marks)

(ii) f(x)=36x4f''(x)=\frac{36}{x^4} (2 marks)


4. (i) 3(x+32)2+1343(x+\frac{3}{2})^2+\frac{13}{4} (3 marks)

(ii) (32,134)(-\frac{3}{2}, \frac{13}{4}) (3 marks)

(iii) 39-39 (2 marks)


5. (i) Correct sketch (2 marks)

(ii) y=2(x+5)2y=\frac{2}{(x+5)^2} (2 marks)

(iii) Stretch scale factor 12\frac{1}{2} parallel to y axis (2 marks)


6. (i) Centre (0,4)(0, -4) and radius 2102 \sqrt{10} (3 marks)

(ii) (2,10)(-2, -10) (2 marks)


7. (i) x<18x<-\frac{1}{8} (2 marks)

(ii) 0x50 \leq x \leq 5 (5 marks)


8. 6x+2y1=06x+2y-1=0 (7 marks)


9. (i) Correct sketch with intersections at (-1.5, 0) and (2, 0) and (0, -6) (5 marks)

(ii) x14x \leq \frac{1}{4} OR x<14x < \frac{1}{4} (either will be marked correct) (3 marks)

(iii) 4.54.5 (4 marks)


10. (i) k=5k=-5 (7 marks)

(ii) Minimum (2 marks)

(iii) (2,27)(-2, -27) (5 marks)


I'll be around to answer questions shortly.


hey, for question 10 iii) i dy/dx the curve(-3x2-6x+9) then equated to gradient of tangent(9) but i ended up getting x=-2.5 and subbing into curve to get -35/8 how many marks will i lose ?
(edited 10 years ago)

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