# FP2

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#1
What topic should I go over in order to do this question?
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1 year ago
#2
(Original post by Maths&physics)
What topic should I go over in order to do this question?
The first part is nothing new in itself - it is just applying things that you already know. In particular, you have to use the chain rule to find the conection between dy/dx and dz/dx - you can then substitute to arrive at the given alternative form.

Even if this is a problem, you can still do (b) if you know how to solve first order differential equations using integrating factors (and if not, that's what you need to go over!).

The last part should then be easy using the substitution from the start of the question.
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1 year ago
#3
(Original post by Maths&physics)
What topic should I go over in order to do this question?
Surprisingly enough, given the question uses the phrase "differential equation" 4 times, the relevant topic is differential equations.

I feel like I'm wasting my breath, but you need to revise the material before attempting the questions. Pretty much every post you make seems to result from you picking a question, trying to solve it, then asking for help, at which point it becomes obvious you don't know any of the underlying material. As I understand it, you are redoing the year, and so you probably think "I know this stuff, I just need the odd bit of help". But from the outside, it's very hard to agree that "you know this stuff" well enough to be attempting questions on it.
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#4
(Original post by DFranklin)
Surprisingly enough, given the question uses the phrase "differential equation" 4 times, the relevant topic is differential equations.

I feel like I'm wasting my breath, but you need to revise the material before attempting the questions. Pretty much every post you make seems to result from you picking a question, trying to solve it, then asking for help, at which point it becomes obvious you don't know any of the underlying material. As I understand it, you are redoing the year, and so you probably think "I know this stuff, I just need the odd bit of help". But from the outside, it's very hard to agree that "you know this stuff" well enough to be attempting questions on it.
Yeah, Iโm sorry, I have actually been over this stuff the other day - itโs in fact the first topic covered on exam solutions in differentiation - a first order differential equation.

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#5
(Original post by DFranklin)
Surprisingly enough, given the question uses the phrase "differential equation" 4 times, the relevant topic is differential equations.

I feel like I'm wasting my breath, but you need to revise the material before attempting the questions. Pretty much every post you make seems to result from you picking a question, trying to solve it, then asking for help, at which point it becomes obvious you don't know any of the underlying material. As I understand it, you are redoing the year, and so you probably think "I know this stuff, I just need the odd bit of help". But from the outside, it's very hard to agree that "you know this stuff" well enough to be attempting questions on it.
this is how I did the question?

it's suppose to be dz/dx - 2z...
Last edited by Maths&physics; 1 year ago
0
1 year ago
#6
(Original post by Maths&physics)
this is how I did the question?

it's suppose to be dz/dx - 2z...
First write down the variable you want to change. It is y and it's derivatives. So in the end you should have no ys or dy/dx.

Next note your change of variables, z=sqrt(y)

Now write each thing you want to change in terms of z and z's derivatives.

Note dy/dx = dy/dz * dz/dx (but dy/dz Can be worked out - remember we don't want to see y).

Finally replace your y functions and derivatives of y with z functions and derivatives of z in the equation given.

This should work for any change of variables question given.
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1 year ago
#7
reducible differential equations. and AS maths differential equations
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