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

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.

(edited 10 years ago)

Reply 1

Majeue

1

Original post by Mr M

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) (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,

I accidentally put k=5 rather than -5 with all the correct working. This meant that i got the wrong quadratic for part 10.iii. however i did the working correctly, equating the differentiated 9x-9 to my quadratic i got from differentiating the cubic in part i, but it turned out to be an unsolvable quadratic due to my incorrect value of k. How many marks would i probably lose? :/
Thanks

(edited 10 years ago)

Reply 2

a10

19

Original post by Mr M

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) (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.

shouldn't 7i be x<-1/8

OP

Original post by Majeue

Mr M,

I accidentally put k=5 rather than -5 with all the correct working. This meant that i got the wrong quadratic for part 10.iii. however i did the working correctly, equating the differentiated 9x-9 to my quadratic i got from differentiating the cubic in part i, but it came to be an unsolvable quadratic. How many marks would i probably lose? :/
Thanks

Lose 1 mark in part (i) and 1 or 2 in part (iii).

Reply 4

queketth

Original post by Mr M

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

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

and (0,-6) was needed for the y axis intercept ?

surely 7i is -1/8

OP

Original post by a10

shouldn't 7i be x<-1/8

Yes sorry typo. I'll fix it.

Reply 7

geekD96

7

what will grade boundaries be like?

Reply 8

eggfriedrice

16

Original post by Mr M

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) (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.

Ohh! Looks like I only dropped one or two marks.

How many marks would you drop if put two answers for the last one. I put -2,-27 and -9,0
I know the second one is incorrect since there's only one one tangent.

Reply 9

edkin

How many marks will you get for finding the two coordinates on the last question but doing no further working

Reply 10

daisyrchds

Hi, if for question 9(i) i got the (1.5,0) and (-2,0) instead, how many marks would i drop? thanks :smile:

also for part 9(iii) i got the correct answer but left it as sqrt(81/4).. do i lose marks for this?

(edited 10 years ago)

OP

Original post by queketth

and (0,-6) was needed for the y axis intercept ?

Thanks. I actually missed that off my working. Will amend.

OP

Original post by daisyrchds

Hi, if for question 9(i) i got the (1.5,0) and (-2,0) instead, how many marks would i drop? thanks :smile:

Probably 2.

Reply 13

username23423

9

Original post by Mr M

Mr M's OCR (not OCR MEI) Core 1 Answers May 2013
9. (i) Correct sketch with intersections at (-1.5, 0) and (2, 0) and (0, -6) (5 marks)

Does this means you won't be penalised for not labelling the intersection with the Y axis?

EDIT: Nevermind, you sneakily edited while I quoted you. I labelled in anyway though so :biggrin: