Current Year 12 Thread Mark VI
Discussion for A-Level students and for those choosing their A-Level subjects.
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Re: Current Year 12 Thread Mark VIx=ap ?(Original post by Blutooth)
That's what I said at interview but no, that's not it. See my previous edit. -
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Re: Current Year 12 Thread Mark VIYeah, except y=ax or x=ay can't remember which(Original post by wcp100)
x=ap ? -
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Re: Current Year 12 Thread Mark VIThat makes the RHS a constant.... if a is constant obv.(Original post by Blutooth)
Yeah, except y=ax -
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Re: Current Year 12 Thread Mark VINo it doesn't(Original post by wcp100)
That makes the RHS a constant.... if a is constant obv.
... but I'm not sure perhaps it's the other one.
Last edited by Blutooth; 03-06-2012 at 13:46. -
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Re: Current Year 12 Thread Mark VINo, a is a variable. You should try to change the differential equation dy/dx to one of the form da/dx.(Original post by wcp100)
Just to clarify, a is a constant? -
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Re: Current Year 12 Thread Mark VIThat explains my previous comment. I thought it was an odd sub.(Original post by Blutooth)
No, a is a variable you should try to change the differential equation dy/dx to one of the form da/dx. -
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Re: Current Year 12 Thread Mark VISorry, I missed that you said if a is a constant.(Original post by wcp100)
That explains my previous comment. I thought it was an odd sub. -
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Re: Current Year 12 Thread Mark VII just can't separate the variables with y=ax.(Original post by Blutooth)
Sorry, I missed that you said if a is a constant. -
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Re: Current Year 12 Thread Mark VIAnd neither can I.(Original post by wcp100)
I just can't separate the variables with y=ax. I'll have to do a few minutes of head-scratching. I'm gonna try xy=a.
Last edited by Blutooth; 03-06-2012 at 14:21. -
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Re: Current Year 12 Thread Mark VIAre you sure my original suggestion doesn't work? In fact are you sure my equation is right?(Original post by Blutooth)
And neither can I. I'll have to do a few minutes of head-scratching. I'm gonna try xy=a.
![-2 \text{ArcTan}\left[\frac{1}{2} \left(2-\frac{2 (-1+2 x)}{x-y[x]}\right)\right]-\text{Log}\left[\frac{\left(2+\frac{(-1+2 x) \left(-2+\frac{-1+2 x}{x-y[x]}\right)}{x-y[x]}\right) (x-y[x])^2}{(-1+2 x)^2}\right]=C[1]+2 \text{Log}[-1+2 x]](http://www.thestudentroom.co.uk/latexrender/pictures/80/8097cea48ac5b78867394dbe720e4320.png "-2 \text{ArcTan}\left[\frac{1}{2} \left(2-\frac{2 (-1+2 x)}{x-y[x]}\right)\right]-\text{Log}\left[\frac{\left(2+\frac{(-1+2 x) \left(-2+\frac{-1+2 x}{x-y[x]}\right)}{x-y[x]}\right) (x-y[x])^2}{(-1+2 x)^2}\right]=C[1]+2 \text{Log}[-1+2 x]")
That is what Wolfram gets.
Edit: By this point I've clearly failed to get into Oxford.Last edited by bananarama2; 03-06-2012 at 14:39. -
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Re: Current Year 12 Thread Mark VI(Original post by wcp100)
Are you sure my original suggestion doesn't work? In fact are you sure my equation is right?
That is what Wolfram gets.
Edit: By this point I've clearly failed to get into Oxford.
100% sure your equation is right.
Nah, I asked some of the people who got in how far they got on this question, and the 2 I asked didn't get asked to solve the differential equation because they didn't get that far with the question. In fact all the people I spoke to at interview couldn't do the whole question, most couldn't do the first part w/o the interviewers basically telling them.
knowing the right sub to use isn't really about mathematical intuition but about what you've come across before. That's why the interviewers just told me the right sub to make.
I'm pretty sure I suggested to the interviewers that we make the sub u=y-x but they told me not to go down that route. I still suspect it's a sub similar to y=ax or something. I've just been eating but as soon as I've finished I'll check it out.Last edited by Blutooth; 03-06-2012 at 14:55. -
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Re: Current Year 12 Thread Mark VIYep. That was a nice question, was it not?(Original post by Blutooth)
I've probably done this question before but if I did it's been so long ago I can't remember. At least a year and a half...Spoiler:Show
I'm now doing a not-so-nice question and I've ended up with something that looks like this for which I have to solve for x in terms of alpha:
where 
.
This is clearly not going to end well and I'm not entirely sure that I've done the right thing to get to this.
Well... all this maths has made me extremely hungry so I'm off to have lunch.Last edited by Maths_Lover; 03-06-2012 at 15:57. -
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Re: Current Year 12 Thread Mark VIThat looks like a STEP questions(Original post by Maths_Lover)
Yep. That was a nice question, was it not?
I'm now doing a not-so-nice question and I've ended up with something that looks like this for which I have to solve for x in terms or alpha:
where .
This is clearly not going to end well and I'm not entirely sure that I've done the right thing to get to this.
Well... all this maths has made me extremely hungry so I'm off to have lunch.
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Re: Current Year 12 Thread Mark VII have refuelled and now I'm ready for some more maths.
It is a STEP question... I am on the last part but I'm going to leave it because I'm not sure I have the right method and solving that beast only to then find out that the equation is incorrect in the first place will aggravate me to no end. I shall ask my previous maths teacher, the Head of Maths, for help when we go back.
STEP is fun but sometimes it makes me want to bury myself in a hole.
Last edited by Maths_Lover; 03-06-2012 at 15:55. -
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Re: Current Year 12 Thread Mark VIWhich question was it out of interest?(Original post by Maths_Lover)
I have refuelled and now I'm ready for some more maths.
It is a STEP question... I am on the last part but I'm going to leave it because I'm not sure I have the right method and solving that beast only to then find out that the equation is incorrect in the first place will aggravate me to no end. I shall ask my previous maths teacher, the Head of Maths, for help when we go back.
STEP is fun but sometimes it makes me want to bury myself in a hole.
I know that feeling! -
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Re: Current Year 12 Thread Mark VISTEP I 2008 question 4 part (ii). Part (i) was a piece of cake but then I went on to part (ii)...
I am not sure whether or not you can treat k as a constant but if you can't then that is even worse than if you can. I treated k as a constant and tried to do the same thing as I did in part (i) and it quickly went pear-shaped and then when I tried to solve that thing, I ended up with
and by this point I just didn't want to carry on...
Last edited by Maths_Lover; 03-06-2012 at 16:18. -
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Re: Current Year 12 Thread Mark VIIt was nice, so nice I fell asleep while latexing it, only to find I had made a mistake when my head hit the keyboard. Doh...(Original post by Maths_Lover)
Yep. That was a nice question, was it not?
I'm now doing a not-so-nice question and I've ended up with something that looks like this for which I have to solve for x in terms or alpha:
...Actually, I didn't fall asleep I just made a mistake.
That is the contradictory nature of mathematics, my friend. -
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Re: Current Year 12 Thread Mark VI(Original post by Blutooth)
It was nice, so nice I fell asleep while latexing it, only to find I had made a mistake when my head hit the keyboard. Doh...
...Actually, I didn't fall asleep I just made a mistake.
That is the contradictory nature of mathematics, my friend.
I did at first - it's so easy to accidentally do something wrong while evaluating the integral.
Indeed it is.
"That one doesn't look that bad - look how short it is!"
*4 pages of crazy algebraic manipulation later.*
"****! @!!#;#!!" 
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Re: Current Year 12 Thread Mark VIYou can treat k as a constant as the variable is arbitrarily set and not related to x.(Original post by Maths_Lover)
STEP I 2008 question 4 part (ii). Part (i) was a piece of cake but then I went on to part (ii)...
I am not sure whether or not you can treat k as a constant but if you can't then that is even worse than if you can. I treated k as a constant and tried to do the same thing as I did in part (i) and it quickly went pear-shaped and then when I tried to solve that thing, I ended up with and by this point I just didn't want to carry on...
... but I'm not sure perhaps it's the other one.
