AQA Core 4 Exam Discussion 14/06/2012 !Poll, paper and unofficial MS (first post)!

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For the differential equation, did anyone get t= 5x(2x-1)^1.5 - (2x-1)^2.5 - 4?

The equation in x that had to be integrated was 15x(2x-1)^0.5, i'm sure...I did it by parts ahah, no idea if it's right :smile:

I did that too!

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Reply 581

Cath-ay

Original post by mollster57

I NEED 60 UMS to get my C overall and get into university.
Anyone have a rough idea of the mark boundaries?
Jan 12 was hard and it was 45 marks for a C, do you think it'll be higher/lower/the same for this paper?

Lower I hope! I found the jan 12 paper okay, even june 2011 wasn't that bad.

Reply 582

lagoom

Original post by Lukee16

For the implicit one, i believe you ended up with 3x=y, which you then put into the original equation to get y=±1 & x=±1/3

I got to 3x=y but then left it as that :frown:

Reply 583

theBLOBlizard

Original post by Lukee16

I done the same as you, but got a different value for +c, think i went wrong somewhere though.

What did you get for C?

Reply 584

rosie17

For those that use integration by parts instead i think its still right and i did it with substitution tinto and put in some values and they equalled exactly the same.

in the question i put my x's to the side of the differential to get..

the integral of 15x(2x-1)^0.5 dx = integral of 1 dt

first with parts...

u=15x dv/dx= (2x-1)^0.5

du/dx= 15 v= 1/3(2x-1)^1.5

uv-integral of v(du/dv)

t =5x(2x-1)^1.5-(2x-1)^2.5 + c

c= -4

i also did it with substitution to get
1.5(2x-1)^2.5 + 2.5(2x-1)^1.5

c=-4

i also put in different values of x to see if they equalled the same and they do so i think both ways are okay to do :smile:

Reply 585

make it snappy

Original post by jammysmt

I did that too!

This was posted from The Student Room's iPhone/iPad App

I got this to!

Bye bye firm choice

Original post by WarpStreak

I got something similar but didn't simplify it i.e had t=15(?) rather than multiplying it out, would i lose marks?? =/

Reply 588

mojopin1

Original post by make it snappy

The stationary points question was hard for me! how were you suppose you do that?

On 8b i got c = 4 or -4.. cant remember the sign, using intergration by parts.
and t to be somthing like 36?

I can't really remember now :tongue:

but you first had to differentiate the equation, one part of it needed the product rule. Then you make your dy/dx = 0. Bottom lines cancels and you're left with Y=... Sub that back into the original equation and you get a quadratic which you have to factor, then you get +- 1/3. Then sub these back into your Y=... to get the stationary points.

Reply 589

kenau

I don't have enough time to check the question that I couldn't finished......
So there must have some careless mistake in there..... :s-smilie:

Hoping the low grade boundary .................
Still have confident to get an A...
The most tricky things is this paper need to use a lot of C3 techique, like 1/cosec x,integration by part etc...

Reply 590

rosie17

what coordinates did people get for b in the vectors question??

Reply 591

WarpStreak

Do people want me to write out my answers? I had time to put quite a few down in my calculator...

Reply 592

LookIt'sPete

In the vector question, for the coordinates of B, I got u = -1/3 and -5/3 and then put it back into the equation for the points on the line.

For the final question, I can't remember what I got for the differential equation, but for the final part, which was the time for the pool to fill up to 2 metres, I got 32.4

Reply 593

mollster57

Original post by WarpStreak

Do people want me to write out my answers? I had time to put quite a few down in my calculator...

Yes please!

Reply 594

rosie17

Original post by WarpStreak

Do people want me to write out my answers? I had time to put quite a few down in my calculator...

ohh yes please :smile:

Reply 595

make it snappy

Sounds like quite a lot of poeple ran our of time for this exam, or at least was panicking at the end trying to finnish of a question.

Did anyone think the marks awared on the vector question was unfair? the first 2 parts of the question were worth hardly no marks but took a fair amount of working out