cosine rule!
a = 2rt7
b = x+2
c = x
A = 60 degrees

substituting those into the cosine rule you ended up with a quadratic
x^2 + 2x - 24 i think
which factorised into (x-4)(x+6)
so x = 4 (as it couldn't be a negative)

Reply 32

__wjk__

Original post by Mr M

I used a computer and it was 314.4 then rounded to 3 s.f.

ah ok, would i lose more than one mark for putting 314.4 and then 315 (3sf)?

Reply 33

Mr M

Study Forum Helper

Original post by cheeky_monkey

for question 3i, i only put three values rather than 4. how many marks would i lose??

Drop 1.

Reply 34

Mr M

Study Forum Helper

Original post by Bwile12

I got x=3 for the first question due to adding incorrectly, still did all the working out through... How many marks would I lose

Drop 1 or 2.

Reply 35

Imirrelevant

What was question 7a and Questions 4?

Reply 36

nega166

Original post by Mr M

Mr M's OCR (not OCR MEI) Core 2 Answers May 2017

1. (i) 4 (4 marks)

(ii)

6 \sqrt 3

(2 marks)

2. (i) 0.715 (4 marks)

(ii) Underestimate because trapeziums lie under the curve (2 marks)

3. (i)

1+4x+7x^2+7x^3

(4 marks)

(ii) 11 (2 marks)

4.

y=2x^{\frac{5}{2}}-5x^2+27

(6 marks)

5. 2.19 (6 marks)

6.

\frac{11}{6}

(7 marks)

7. a) 314 (4 marks)

b) i) Show

y=2x^2-1

(4 marks)

ii) x=2 and y=7 or x=3 and y=17 (4 marks)

8. a)

a=-24

(5 marks)

b)

a=30-14\sqrt2

(6 marks)

9. (i) Show and

f(x)=(2x-1)(2x^2+x+5)

(4 marks)

ii) a) Show (4 marks) b)

\theta=\frac{\pi}{12}

and

\theta = \frac{5\pi}{12}

and

\theta=\frac{13\pi}{12}

and

\theta=\frac{17\pi}{12}

(4 marks)

Heck. 9 was wrong. Now fixed.

Hello Mr. M, I have a few questions regarding my paper:

1. For question 1a) I got a quadratic but it was a wrong quadratic, leading me to the wrong value of x. How many marks would I lose here?
2. I then used this incorrect value of x to calculate the area in 1b - how many marks would I lose?
3. For 2ii) I didn't draw 4 trapezia but I did draw the trapezia (maybe 3 or 5) and said that the tops of them were below the curve. Would I lose any marks for not drawing exactly 4?
4. For 7a) I might have said 315 as a result of incorrect rounding - how many marks would I lose here?
5. For 8b) I correctly identified r as root 2, then tried to plug it in but got an incorrect value for a, however this involved a 127, which is only 1 away from the 126 which 14 is a factor of, so I'm not sure where I went wrong there, but how many marks would I lose?
6. Lastly, for 9iib) I correctly doubled the given range, but forgot to find the extra 2 solutions - how many marks would I lose here?

Thanks in advance, as always.

Reply 37

SamLopezF

Hi everyone what was question 6?

Reply 38

SamLopezF

Original post by Mr M

Mr M's OCR (not OCR MEI) Core 2 Answers May 2017

1. (i) 4 (4 marks)

(ii)

6 \sqrt 3

(2 marks)

2. (i) 0.715 (4 marks)

(ii) Underestimate because trapeziums lie under the curve (2 marks)

3. (i)

1+4x+7x^2+7x^3

(4 marks)

(ii) 11 (2 marks)

4.

y=2x^{\frac{5}{2}}-5x^2+27

(6 marks)

5. 2.19 (6 marks)

6.

\frac{11}{6}

(7 marks)

7. a) 314 (4 marks)

b) i) Show

y=2x^2-1

(4 marks)

ii) x=2 and y=7 or x=3 and y=17 (4 marks)

8. a)

a=-24

(5 marks)

b)

a=30-14\sqrt2

(6 marks)

9. (i) Show and

f(x)=(2x-1)(2x^2+x+5)

(4 marks)

ii) a) Show (4 marks) b)

\theta=\frac{\pi}{12}

and

\theta = \frac{5\pi}{12}

and

\theta=\frac{13\pi}{12}

and

\theta=\frac{17\pi}{12}

(4 marks)

Heck. 9 was wrong. Now fixed.

Hi everyone what was question 6?

Reply 39

Alomak

Dear Mr M,

How many marks would I lose:

For q1, I used the cosine rule and got x=3, then used this value to work out the area for part 2.

For 8b) I got r as root 2, but failed to plug it back in correctly, so did not get the simplified root form and instead could only round the answer up.

Thanks a lot