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Mr M's OCR (not OCR MEI) Further Pure 1 Answers May 2016

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For 3ii, i accidently substituted a+b on the denominator instead of ab (even though i wrote ab) so got the answer as -1/k with the rest of the working correct. How many marks do you reckon ill lose? Thanks in advance

Reply 41

btsx

for the shear question is it okay to say a shear parallel to the x-axis by 3 units?

Reply 42

Mr M

Study Forum Helper

Original post by beelal

Probably only drop 1.

Reply 43

Mr M

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Original post by HGT98

For the method of differences (q8) I forget to half the answer in ii), so carried this through to the next part of the question iii) - but I did write answers as a single fraction. Also for finding z (q2) I used -sqrt(3) - 3i instead of a positive sqrt(3) and also carried this onto the next part of the question. How many marks would I lose over these questions as a rough estimate? Thanks!

Drop 1 mark in each case I expect.

Reply 44

Mr M

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Original post by btsx

for the shear question is it okay to say a shear parallel to the x-axis by 3 units?

Drop 1 mark.

Reply 45

Mr M

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Original post by 0704

How many marks do you think I will lose if I put root 3 +3i for question 2i and therefore got an incorrect answer for part ii as I rationalised the wrong thing?

Drop 1.

Reply 46

lordkronos258

Q3i) i got wrote -1/k as -x/k and so for 3ii) got x^2/k^2
Q2ii) misread the question and thought it was + 5i instead of - 5i
will i get any marks on 2ii or 3ii?
thanks for all the help

Reply 47

2807

For 10(iii) do you get a mark for subbing in z=(1/u^2) and getting the equation given in the question?

Reply 48

Sweens_a

What actually was question 8? I thought i'd managed to do it right but clearly not haha.

Reply 49

Mr M

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Original post by 2807

For 10(iii) do you get a mark for subbing in z=(1/u^2) and getting the equation given in the question?

Yes.

Reply 50

Mr M

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Original post by lordkronos258

Q3i) i got wrote -1/k as -x/k and so for 3ii) got x^2/k^2
Q2ii) misread the question and thought it was + 5i instead of - 5i
will i get any marks on 2ii or 3ii?
thanks for all the help

Yes you'll probably lose 4 marks in total over the 2 questions.

Reply 51

Nl1998

Hi,

How many marks do you think I'll lose if:
For Q8ii & iii, I forgot to do the 1/2 and then the next part used the previous answer
For Q10iii, I only got the 2 solutions rather than the 4.

Also, for Q10ii, did you just have to sub in the root and then get 0 to get the mark?

And how did you do Q6iii? I did it off sight and I think I got different answers to you.

Thank you in advance!

Reply 52

jjjjjjjjjjjj96

I'm coming out with the answer (5n + 4) / (6n + 3). Can you explain how you derived the answer for 8iii

Reply 53

Buymoria

Original post by Mr M

Mr M's OCR (not OCR MEI) Further Pure 1 Answers May 2016

1.

\displaystyle \frac{n(2n+3)(n-1)}{2}

(5 marks)

2. (i)

\sqrt{3}-3i

(2 marks)

(ii)

\displaystyle \frac{-1+4\sqrt{3} i}{49}

(5 marks)

3. (i)

\displaystyle \alpha + \beta = -\frac{1}{k}

and

\displaystyle \alpha \beta = 1

(1 mark)

(ii)

\displaystyle \frac{1}{k^2}

(5 marks)

4. (i)

\begin{pmatrix} 5a-3b & 10 & 0 \end{pmatrix}

(2 marks)

(ii)

\begin{pmatrix} 6b-5 \end{pmatrix}

(2 marks)

(iii)

\begin{pmatrix} 6a & 12 & 18 \\4a & 8 & 12 \\-a & -2 & -3 \end{pmatrix}

(2 marks)

5. Proof (4 marks)

6. (i)

\displaystyle |z-3-3i|=\sqrt 5

(4 marks)

(ii) Sketch (2 marks)

(iii)

2+5i

and

4+i

(3 marks)

7. (i) Shear with x axis invariant taking the point (0, 1) to (3, 1) (2 marks)

(ii)

\begin{pmatrix} 0 & -1 \\-1 & 0 \\ \end{pmatrix}

Reflection in the line

y=-x

(6 marks)

8. (i) Show (1 mark)

(ii)

\displaystyle \frac{n}{3(2n+3)}

(6 marks)

(iii)

\displaystyle \frac{1}{2(2n+1)}

(3 marks)

9. (i) Show (3 marks)

(ii) Determinant = 0 when a = 3 so no unique solution. The equations are consistent because 3 x equation 3 - equation 1 = equation 2. (3 marks)

10. (i)

5+4i

and

-5-4i

(6 marks)

(ii) Show (1 mark)

(iii)

\displaystyle \pm \frac{5}{41} \pm \frac{4i}{41}

(4 marks)

How many marks do you think you'd lose for having a 8ii of twice the correct answer (forgot to divide by 2 at the end) and then using that incorrect answer in 8iii (though my 8iii would have been correct had 8ii been correct)

Reply 54

Mr M

Study Forum Helper

Original post by Nl1998

8ii and iii. Drop 1 I expect.

10iii. Drop 1.

10ii. That's right.

6iii. I cheated and used a computer.

Reply 55

Mr M

Study Forum Helper

Original post by jjjjjjjjjjjj96

I'm coming out with the answer (5n + 4) / (6n + 3). Can you explain how you derived the answer for 8iii

\displaystyle \sum_{r=n}^\infty = \sum_{r=1}^\infty - \sum_{r=1}^{n-1}

Reply 56

CC21231

Would you be able to put question 8 on here because I would like to try it again?
Also for 10 iii what did you do after subbing z=1/u^2 into the equation

Reply 57

jjjjjjjjjjjj96

Original post by Mr M

\displaystyle \sum_{r=n}^\infty = \sum_{r=1}^\infty - \sum_{r=1}^{n-1}

Please can you show how you got your answer?

Reply 58

jonnypiercy

what was the final result you had to get for the proof by induction??

(edited 7 years ago)

Reply 59

GcseLad-_-

Hi sir, i hope you could answer a few questions of mine:
For 6ii i drew the correct circle but somehow got the line 'l' wrong and drew the perpendicular bisector of the origin and the centre of the circle
And then for 6iii i worked out the intersection points by looking at them and checking they were root 5 form the circles centre, but i did this according to the diagram i drew woud i get ecf marks?
Finally for the last part of the last question, i figured out every root in a unsimplied form eg. 1/(5+4i) but then wrote eg 1/5+1i/4 and split up the fraction for every root which was stupid, how many marks do you think i will get out of 4?
Id appreciate your help Mr M :smile: