OCR (not MEI) C2 - Wednesday 20th May 2015

y = -3 + 2root(x+4)
(y + 3)/2 = root (x+4)
x+4 = (y+3)(y+3)/4
x+4 = (y^2 + 6y + 9) / 4
x = 1/4(y^2 + 6y + 9) - 4
x = 1/4(y^2 + 6y - 7)

Then integrate as dx/dy with the limits of y=3 and y=1 and you should get the answer they want. Hope you can follow that okay :smile:

Hi. When I did this question, I calculated the area from the curve to the x axis and then subtracted this from the area of the rectangle to find the area of that little area B. Do you think this is acceptable considering the context of the question?

Reply 41

c223

OP

2

Original post by gabby07

Hi. When I did this question, I calculated the area from the curve to the x axis and then subtracted this from the area of the rectangle to find the area of that little area B. Do you think this is acceptable considering the context of the question?

When we did this as a mock, a couple of my class did it this way and my teacher seemed to think that you'd lose marks for not writing the function in the form x=f(y) like it asks for. The mark scheme was posted on the previous page so you could try to work out what you'd be given from that :smile:

Reply 42

gabby07

11

Original post by chloe-jessica

When we did this as a mock, a couple of my class did it this way and my teacher seemed to think that you'd lose marks for not writing the function in the form x=f(y) like it asks for. The mark scheme was posted on the previous page so you could try to work out what you'd be given from that :smile:

Yeah I thought so. The only reason I think I get confused in differentiation between to lines/ a line and a curve is when to take away the bottom one from the top one and when to just leave it (as you do in this question).

Reply 43

c223

OP

2

Original post by gabby07

Yeah I thought so. The only reason I think I get confused in differentiation between to lines/ a line and a curve is when to take away the bottom one from the top one and when to just leave it (as you do in this question).

Because this question was asking for an area between a curve and the y-axis, it was easiest to integrate y=... I'd just be careful and if it says to change the function into that form, do it. It's basically because at C3 you learn more about integration and the function they gave you in this question needs to be integrated in a different way (well technically this one was alright because of the numbers they'd chosen, but in the future this may not be true). For example, you can't integrate (7x+4)^4 without either expanding or using a rule you learn next year :smile:

Reply 44

Peppercrunch

14

Can't wait for June 3rd, after S1.

No more maths after that as I'm dropping it in September.

Reply 45

Matthewdang

1

Haha. Same here. How you feeling about s1? To me that's the hardest and most confusing

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Reply 46

Peppercrunch

14

Original post by Matthewdang

Haha. Same here. How you feeling about s1? To me that's the hardest and most confusing

Posted from TSR Mobile

S1 is fine for me, except from permutations and combinations, as well as binomial and geometric distribution.

In my opinion the order goes (easiest to hardest):
C1<S1<C2

Reply 47

sandpitturtle

6

Original post by Peppercrunch

S1 is fine for me, except from permutations and combinations, as well as binomial and geometric distribution.

In my opinion the order goes (easiest to hardest):
C1<S1<C2

C2 easiest, then C1 then stats for me :wink:

Reply 48

scrlk

7

Original post by chloe-jessica

y = -3 + 2root(x+4)
(y + 3)/2 = root (x+4)
x+4 = (y+3)(y+3)/4
x+4 = (y^2 + 6y + 9) / 4
x = 1/4(y^2 + 6y + 9) - 4
x = 1/4(y^2 + 6y - 7)

Then integrate as dx/dy with the limits of y=3 and y=1 and you should get the answer they want. Hope you can follow that okay :smile:

Thanks.

Hopefully this years C2 paper will be nicer than last years.

Reply 49

c223

OP

2

Original post by scrlk

Thanks.

Hopefully this years C2 paper will be nicer than last years.

Yeah last years was one of the harder ones which I've seen. Hopefully that means they'll make up for it with an easy one this year!

Reply 50

Abbie2511

Anyone else got D2 straight after? Not looking forward to that morning at all😫

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Reply 51

hallo.C

4

Original post by Abbie2511

Anyone else got D2 straight after? Not looking forward to that morning at all😫

Posted from TSR Mobile

I have D2 straight after, I'm fearing for my further maths grade with that paper. I absolutely hate it

Reply 52

Abbie2511

Original post by hallo.C

I have D2 straight after, I'm fearing for my further maths grade with that paper. I absolutely hate it

I messed up FP1, which I supposedly find the easiest, so I need to get every mark I can in D1 and D2 which is so annoying

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Reply 53

ss334

Original post by Peppercrunch

S1 is fine for me, except from permutations and combinations, as well as binomial and geometric distribution.

In my opinion the order goes (easiest to hardest):
C1<S1<C2

who can even permutation or combination

Reply 54

gabby07

11

Hi can I just check with someone, if you are using the formula for S_nfor a Geometric Progression:

\frac{a(1 - r^n)}{1-r}

with a value of r which is greater than 1, do you switch the equation to:

\frac{a(r^n - 1)}{r-1}

Is this correct??!
Thanks :smile:

Reply 55

hallo.C

4

Original post by Abbie2511

I messed up FP1, which I supposedly find the easiest, so I need to get every mark I can in D1 and D2 which is so annoying

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We don't do D1 until core maths in Year 13 so I'm doing D2 without having been taught D1

Reply 56

Fandalf

2

Everybody ready for a horrible paper. Ocr has been following its reputation of last year. First a nice Core 1 paper, than a TERRIBLE physics paper and now we can expect a bad core 2 paper