OCR (not MEI) C1 13/05/13

Dy/dx=-3x^2+6x+4-k
k=-5 so dy/dx=3x^2+6x+9

3x^2+6x+9=9
3x^2+6x=0
3x(x+2)=0
x=0 or x=-2

I did this wrong because instead of doing 4-(-5) while differentiating I did 4-5 so go -1 on the end instead of 9 which gave me a quadratic with no real routes. So I couldn't attempt to find x or y.

How many marks will I lose?

How

I put the values of x and y into the original equation to see if they satisfied it. Putting x = -2 into the equation gave y = -27. The other value for x did not satisfy the equation and gave a different value for y.

Not x-1.

you divide by 1-x

I think you get something like:

y = 9x -9 = -9(1-x)
y = (1-x)(x^2+4x+k)

So -9 = x^2+4x+k
Since k = -5

0 = x^2+4x+4 or (x+2)^2, which shows the repeated root.

At least thats how i did it.

Yup, I got 9/2 too.

Do you even get 'error carried forward' marks in A level?

Do you know the highest grade boundary we ever had?

Ah I did not think of that. you're probably right.

i did something very similar. Instead of making it equal to -3 i did dy/dx and then put in -3 for x and got some wierd answer which then made the part 3 completly wrong
will there be method marks for this?

for the last part i know you had to equate the dy/dx of the curve to 9 and solve to get x. i did this but got 2 x coordinates so i didnt know which one to choose and stopped there. how many marks out of the 5 do you think i would have gotten?? and could anyone explain what you had to do after that step?

Do you know the highest grade boundary we ever had?

****, left it as root 81/4. Will i lose the answer mark?

Posted from TSR Mobile

can we compile a question paper together on here if we're allowed? these answers will be pretty useless unless everyone remembers what they wrote, and i'm sure not everyone will =/ i have a bad memory

Which minimum point?

for the last part i know you had to equate the dy/dx of the curve to 9 and solve to get x. i did this but got 2 x coordinates so i didnt know which one to choose and stopped there. how many marks out of the 5 do you think i would have gotten?? and could anyone explain what you had to do after that step?

I did the same, and put down both we will lose 1-2 marks maximum. Surely wait for mr m for a mark scheme?


Posted from TSR Mobile

For the circles question, was the centre - (0,-4) or (-4,0)???

For the circles question, was the centre - (0,-4) or (-4,0)???

Someone please put my mind at ease out of 12 (have a guess) how many method marks would I get???

for the last part i know you had to equate the dy/dx of the curve to 9 and solve to get x. i did this but got 2 x coordinates so i didnt know which one to choose and stopped there. how many marks out of the 5 do you think i would have gotten?? and could anyone explain what you had to do after that step?

I would guess 6-7 provided your method was correct bar the arithmetical error


Posted from TSR Mobile

Hopefully it's just one mark, I was hoping for 100% >.> darn.