OCR FP1 Friday May 16th 2014

Original post by Knowing

wow never thought of doing it like that. you've just improved my life.

Reply 82

bobbyford

Original post by TheProblematique

√-36 is the same as the √(-1 x 36). √-1 is i and √36 is 6, therefore √-36 is the same as 6i. (4±6i)/2 is 2±3i

thank you very much, I was looking at it in completely the wrong way!

Does anyone have any tips for proof my induction questions? they are the only other ones which I struggle on

Reply 83

destinedtofail:(

5ii) june 2009, i dont know how to obtain -70 as a answer using sum of roots and products

Reply 84

Original post by bobbyford

thank you very much, I was looking at it in completely the wrong way!

Does anyone have any tips for proof my induction questions? they are the only other ones which I struggle on

no problem. Look at the fp1 text book because it has loads of examples on induction questions which I found quite helpful. What exactly is it that you struggle with in induction?

Reply 85

Stakesby

Original post by alow

My record is 18 minutes for FP1 :colone:

To be fair, it was an easy paper, I usually average 25 mins. Plenty of time for checking my answers :lol:

Oh yeah, my record is 12.25 seconds.
My average is like 21.3 ish seconds tho.

Posted from TSR Mobile

Reply 86

scrlk

7

Original post by TheProblematique

Everyone's been so helpful today :smile:

I have another question.

a shear parallel to the x-axis is represented by a matrix that looks like this where k is an integer

1 k
0 1

so if k is 4, is the scale factor of the shear 4 as well? Do shears even have scale factors?

Please correct me if I am wrong but that looks like a combined transformation matrix where X = AB where A and B are the respective shear and scale factor matrices?

Don't quote me on it though, I'm not an expert. :tongue:

Reply 87

Original post by Stakesby

Oh yeah, my record is 12.25 seconds.
My average is like 21.3 ish seconds tho.

Posted from TSR Mobile

Okay...

Reply 88

bobbyford

Original post by destinedtofail:(

5ii) june 2009, i dont know how to obtain -70 as a answer using sum of roots and products

it's a method of differences question?

Reply 89

Original post by destinedtofail:(

5ii) june 2009, i dont know how to obtain -70 as a answer using sum of roots and products

Using the method a certain genius just showed me:

Reply 90

Original post by destinedtofail:(

5ii) june 2009, i dont know how to obtain -70 as a answer using sum of roots and products

Use the substitution and find a cubic in u. Should be obvious from there.

Reply 91

Original post by Stakesby

Oh yeah, my record is 12.25 seconds.
My average is like 21.3 ish seconds tho.

Posted from TSR Mobile

Were you trying to imply that you don't believe the people that are saying they did the paper in such little time or was it a typo and you actually meant to put minutes instead of seconds.

(edited 9 years ago)

Reply 92

Knowing

Original post by destinedtofail:(

5ii) june 2009, i dont know how to obtain -70 as a answer using sum of roots and products

Imagine a cubic:

ax^3 + bx^2 + cx + d, with roots x,y,z

then the sum of product in pairs would be c/a.

(so it would be -70/1 = -70)

Reply 93

MasterOfTheSwag

Original post by TheProblematique

Everyone's been so helpful today :smile:

I have another question.

a shear parallel to the x-axis is represented by a matrix that looks like this where k is an integer

1 k
0 1

so if k is 4, is the scale factor of the shear 4 as well? Do shears even have scale factors?

I think its better to say 'shear x axis invariant that maps the point (0,1) to (x,y)'. So they don't really have a scale factor, you should give an example of a point that it maps (1,0) or (0,1) to. If that makes sense.

Reply 94

bobbyford

Original post by TheProblematique

no problem. Look at the fp1 text book because it has loads of examples on induction questions which I found quite helpful. What exactly is it that you struggle with in induction?

Just get really confused with how to go about different questions in different papers, I'll have a good read of the examples, thanks

Reply 95

Original post by MasterOfTheSwag

I think its better to say 'shear x axis invariant that maps the point (0,1) to (x,y)'. So they don't really have a scale factor, you should give an example of a point that it maps (1,0) or (0,1) to. If that makes sense.

Oh okay, thank you :smile:

Reply 96

Knowing

Pretty sure the mark schemes accept s.f. for shears as well though :tongue:

Reply 97

MasterOfTheSwag

Okay to quote from a markscheme:
'Shear, x axis invariant or parallel to x-axis eg image of (1, 1) is (3, 1) SR allow s.f. 2 or shearing angle of correct angle to appropriate axis'

So yes scale factor is okay but I think saying the image of (1,0) or whatever is safer anyway.

Reply 98

Original post by Knowing

Pretty sure the mark schemes accept s.f. for shears as well though :tongue:

I read in one MS that you can also give the angle of the shear.

Reply 99