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

MR M, what was question 7ii and how did you go about it? If I can remember correctly I found the min point using dy/dx and then just said x<min point (cannot remember co-ordinate).

I appreciate you putting up these answers


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Mr. M, if I did all the correct workings for 10i but got k = 4, then did all the correct workings for 10iii but then got the wrong coordinates, how many marks would I lose? Would I get all the marks for ECF, or if not, how many would I lose?

Can someone please explain this to me (ii) (5 marks) , I think I got that and then changed it to x>0 or x<5 , how many marks will I lose?

could you maybe take a photo of the paper and post it?

Lose 1.

what was 6ii and 9iii I forgot the questions

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.

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.

Your method is ok.

Does anyone roughly remember the questions for 4iii and 7i, I'm not exactly sure what answer i put and i feel it may help jog my memory with the question, other than these I feel i maxed the paper yey

for the question on the radius and center of a circle i got the center correct but for the radius i put
(24-16)^1/2 instead of (24+16)^1/2 and hence ended up with 8^1/2 as my radius. I was wondering how many marks i will drop out of 3? Also i got all the other questions right but i really need to get 100 ums on this pape,r does dropping 1 or 2 marks now mean i cant get 100?

7ii) Solve $(2x-4)(x-3) \leq 12$

Expand the brackets and simplify (make one side of the inequality zero). Sketch the quadratic inequality and state the answer.