[TenOfThem]

Just a couple of questions on validity of methods

First
In the Jan 2012 paper there was a question that gave 3 sets of co-ordinates and a transformation matrix and asked for the vertices of the image

Now I did matrix x (x,y) and found a general (x',y') ... then wrote down the new vertices

The mark scheme says I should have done correct matrix multiplication for at least 2 of the points

Now, clearly I get the A marks but will I miss the M marks?



Second
In the same paper we were given an imaginary root of a cubic and asked for the other roots, now the conjugate is fine but I found the real one by inspection ... the mark scheme shows multiplication of the imaginaries etc

So A marks fine but M marks?




I am supporting my daughter on this syllabus so do not want to steer her wrong

[dragonkeeper999]

I did FP1 MEI - not edexel/ AQA - but for my sylabus it was perfectly acceptable to find the correct answer by any method, as long as you show some workings, eg writing out the multiplication of the imaginary root and complex conjugate and then specifically stating that you will find the other root by inspection, showing the workings for this - multiplying out the relevent bits.
e.g. (X^2 + 3X + 2)(aX + b) = 3X^3 + 12X^2 + 15X + 6,
"solve by inspection",
aX x x^2 = 3X^3, "therefore a=3,
2b = 6, therefore b=3
therefore the other root is -3/3 = -1
not sure about your first question though...

[TenOfThem]

(Original post by dragonkeeper999)
I did FP1 MEI - not edexel/ AQA - but for my sylabus it was perfectly acceptable to find the correct answer by any method, as long as you show some workings, eg writing out the multiplication of the imaginary root and complex conjugate and then specifically stating that you will find the other root by inspection, showing the workings for this - multiplying out the relevent bits.
e.g. (X^2 + 3X + 2)(aX + b) = 3X^3 + 12X^2 + 15X + 6,
"solve by inspection",
aX x x^2 = 3X^3, "therefore a=3,
2b = 6, therefore b=3

thing is, I just looked at the original cubic, thought ... hmmm 2 seems good, tried f(2) in my head and got zero so wrote down 2

[dragonkeeper999]

(Original post by TenOfThem)
thing is, I just looked at the original cubic, thought ... hmmm 2 seems good, tried f(2) in my head and got zero so wrote down 2

As long as you show you substituting it into the original equation that should be fine. (little hint - graphical calculators have this amazing polynomial solver function, just input the equation and press enter - supports both real and imaginary roots... however, because of this, it is essential to show all your working to show the examiner you know how to solve the equation otherwise the examiner will assume/ know you've done this)

[TenOfThem]

(Original post by dragonkeeper999)
As long as you show you substituting it into the original equation that should be fine. (little hint - graphical calculators have this amazing polynomial solver function, just input the equation and press enter - supports both real and imaginary roots... however, because of this, it is essential to show all your working to show the examiner you know how to solve the equation otherwise the examiner will assume/ know you've done this)

hmmmm, thanks

I may suggest that saying f(2) = 0 is needed then



For other teacher who do teach Edexcel (or confident Edexcel students) ... do you have thoughts

[raheem94]

(Original post by TenOfThem)
hmmmm, thanks

I may suggest that saying f(2) = 0 is needed then



For other teacher who do teach Edexcel (or confident Edexcel students) ... do you have thoughts

I don't have much idea about the marking, i only did 1 FP1 past paper before taking this exam in jan 2012.

I don't exactly remember how i did the cubic question, but i am quite sure that i did it in the following way,

The 2 complex roots are

So by using these roots we can form a quadratic



So the quadratic is,

Now by using long division, divide

This will give the other root.

Regarding the matrices question, i don't know much about its marking. It was the question that cost me full marks in the exam, i just wrote the answer as rather than

[raheem94]

(Original post by TenOfThem)
hmmmm, thanks

I may suggest that saying f(2) = 0 is needed then



For other teacher who do teach Edexcel (or confident Edexcel students) ... do you have thoughts

If you state f(2)=0 and then z=2, you will get full marks.

See the mark scheme:




Read the part at the end(written in bold).

[TenOfThem]

(Original post by raheem94)
If you state f(2)=0 and then z=2, you will get full marks.

See the mark scheme:




Read the part at the end(written in bold).

*Must Scroll Down*


Thanks for that

[TenOfThem]

(Original post by raheem94)

Regarding the matrices question,

You see ... I would expect the student to recognise the reflection in y=x so simply write down the new vertices

[raheem94]

(Original post by TenOfThem)
You see ... I would expect the student to recognise the reflection in y=x so simply write down the new vertices

I don't think it is worth to take a risk in such papers.

This paper could easily have been completed in 45mins with full working, so there in no point in trying to leave some working.

And if they deduct marks for it, you know what will it convert into UMS, to get 80UMS(A grade) we needed 69/75 in this paper!!

Complete test of accuracy rather than ability!

[TenOfThem]

(Original post by raheem94)
I don't think it is worth to take a risk in such papers.

Yes, I guess my point is that in AQA ... the question would have been "write down the vertices of the image"

No working out required