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

Q4) that's fine

Q5) lose 1 mark

I've provided a link to the correct graph on wolfram alpha a few pages ago.

No idea about grade boundaries.

Get one or two marks for finding P.

Hello, for the last part of the last question, I did all of the correct working up until the last part where I got to the quadratic equation and factorised it but didn't put what x or y equaled (so no coordinate so I will lose the answer mark but will I get credit for the working up to that point?) but then I doubted myself and tried a different method afterwards which didn't come to an answer (as the method I did first was right) and I didn't cross out my first correct method but will I get penalised for then including a wrong method afterwards even though the second method didn't come to an answer either? Or will they just ignore my second wrong method and give me a few method marks for t hr first correct method or will I get 0 marks for that question?? Really worried as I need an A because this is a resit. Also, for the question where you had to find the length, I put "the square root of 81/4" but then afterwards instead of simplifying that down to just 9/2 I put "9/2 or -9/2" will I still get marks for that question or will the penalise me for including a wrong answer with my right answer and mark the whole question wrong??!*

Thank you! And for the last question if I had the correct method throughout but made arithmetic errors which were crazily stupid in getting me k=49 I should lose about 4? I expanded the brackets, then dy/dx=0 at x=-3 so subbed that and worked out k

for the second part I got the answer of minimum because d2y/dx2 was greater than 0 it was 12 I think would I still get the marks despite wrong value for x?

Finally for the last part, if I made gradient of curve=gradient of tangent so my dy/dx value equal to 9 and tried to factories how many marks would I lose? It was impossible with the values I had though

sorry about the number of questions but really appreciate all the help

thank you

Is that the same if I calculated the midpoint of PQ by mistake?


Posted from TSR Mobile

Hi Mr M
For question 9 where we had to find K i got k to be -6 instead. How many marks do you think i would get...if i just added up wrong at the end.

Also i did have root 81/4 but at the last minute i took off the root sign and put it to just 81/4 how many marks would i lose??

For the completing the square question then finding the coordinates of minimum point if i completed the square wrongly....then would i get no marks for the miminum point part if i used what i got in the complete the square part???

Thank you

For question 5)ii). I put y=2/(x^2)+5. Will I get 1 mark for this because of M1? Also for the radius of the circle, I put root40 instead of 2root10; will I still get the marks?

Mr M? I did all the revision I can, i understood all the questions. How would you avoid silly mistakes? And how can I prepare for questions like the last question of Core1 yesterday? A question with an answer I have never seen before, with two values of x and got it wrong in the end. Where can I go to do really-difficult questions like those. If you were a student, How would you prepare for Core2 this Friday?

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


1. (i) $12 \sqrt 5$ (2 marks)

(ii) $4 \sqrt 5$ (1 mark)

(iii) $5 \sqrt 5$ (1 mark)


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


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

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


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

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

(iii) $-39$ (2 marks)


5. (i) Correct sketch (2 marks)

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

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


6. (i) Centre $(0, -4)$ and radius $2 \sqrt{10}$ (3 marks)

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


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

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


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


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

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

(iii) $4.5$ (4 marks)


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

(ii) Minimum (2 marks)

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


I'll be around to answer questions shortly.