OCR (not-MEI) FP1 - Friday 20th May 2016

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Let's try making a community MS again.
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Reply 41

sdhand

Thankfully I don't think that paper was too bad. (Nothing like the horrendous M2 from Wednesday). I'll have dropped a mark for sure on the intersection points of the bisector and the circle on the argand diagram question because I couldn't remember how to do it, but everything else was fine.

Original post by Gander01

The roots of the z after the substitution were 9+40i and 9-40i I believe, so you needed to use both other parts of the question to get a solution. Mine did involve some nasty fractions though, something over 41 I think, so I doubt I got it fully correct.

I can't remember my exact answer, but got a similar fraction, so that sounds right to me.

Reply 42

sdhand

Posting the questions I remember - Starting to forget them already, might leave it at this for now, hopefully it helps at least.

Question 1: Find The sum from r=1 to n of (3r+1)(r-1) in terms of n

Question 2 i: Find z given arg(z) = - (1/3) pi and mod z = 2 sqrt(3) (unsure about this one, not sure I remembered the modulus correctly)
ii: 1/(z*-5i)^2

Question 3: This was some simple matrix arithmetic, I can't remember the values in the matrices so if anyone can that would be appreciated. There were 3 matrices, A and B being 1 by 3 and C being 3 by 1. The first part was something like 2A+3B

Question 4: Find the square roots of 9+40i, and show that it is a root of x^2+18x+1681=0, hence find the roots of 1+18u+1681u^2

(edited 7 years ago)

Reply 43

Andy98

It was awful

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Reply 44

CC21231

I think I made so many stupid mistakes

Reply 45

SonicTails19

Question 6 was the most confusing for me.
I think I got |z - 3 - 3i| = 5 for the equation, and 1+4i and 5+2i for the point of intersections.
Did anyone else get those answers?

(edited 7 years ago)

Reply 46

CC21231

Original post by SonicTails19

Question 6 was the most confusing for me.
I think I got |z - 3 - 3i| = 5 for the equation, and 1+4i and 5+2i for the point of intersections.
Did anyone else get those answers?

I got root 5 as radius

Reply 47

CC21231

Did everyone get q is reflection in the line y=-x

Reply 48

Mathematicus65

Original post by Bobby21231

I got root 5 as radius

Correct it was root5 radius because the diameter was 2root5

Reply 49

Stylesw

Original post by Bobby21231

Did everyone get q is reflection in the line y=-x

Pretty sure that's what I put

Reply 50

Mathematicus65

Original post by Bobby21231

Did everyone get q is reflection in the line y=-x

Yes that's what I got.

Reply 51

CC21231

Original post by Mathematicus65

Yes that's what I got.

Original post by Stylesw

Pretty sure that's what I put

Yay I might get some marks :smile:

Reply 52

mark scheme

One of the easiest papers i think for 90 UMS it will be about 110%

Reply 53

sdhand

Original post by SonicTails19

Question 6 was the most confusing for me.
I think I got |z - 3 - 3i| = 5 for the equation, and 1+4i and 5+2i for the point of intersections.
Did anyone else get those answers?

First part I got |z-(3+3i)|=sqrt(5) for. That's the question which I struggled on though, so don't take my word for it.

IIRC the question was that A= 1+2i and B= 5+4i so that AB is the diameter of a circle.

I got the center as (5+1)/2, (4+2)/2 = 3,3 and the radius as sqrt((3-1)^2+(3-2)^2))
Hence |z-(3+3i)|=sqrt(5)

I couldn't do the intersection of the bisector though.

Reply 54

Oooskar

I think for 6 it was actually 1+18u^2+1681u^4, I also can't remember if the 18 was a plus or minus

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Reply 55

drandy76

Original post by sdhand

Got the same for that, remember my two points of intersection were 2root 5 apart from one another and so I think they were correct, 4+i was one of them I think

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Reply 56

Buymoria

Is it just me or will those boundaries be disgustingly high?

Reply 57

Oooskar

It was plus, just checked on wolfram alpha and this is what I put so I'm fairly certain the answers were +/-((4/41)+(5/41)i) and +/-((4/41)-(5/41)i)

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Reply 58

airborne454

Tbh the paper was relatively harder so I reckon grade boundaries will be about 57/72. Also, How many marks do I lose for not rationalizing my answers to the very last question?

Reply 59

CC21231

Original post by airborne454

Tbh the paper was relatively harder so I reckon grade boundaries will be about 57/72. Also, How many marks do I lose for not rationalizing my answers to the very last question?