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(Original post by

What topic should I go over in order to do this question?

**Maths&physics**)What topic should I go over in order to do this question?

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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#3

(Original post by

What topic should I go over in order to do this question?

**Maths&physics**)What topic should I go over in order to do this question?

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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(Original post by

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.

**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.

Thank you for your patience.

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**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.

it's suppose to be dz/dx - 2z...

Last edited by Maths&physics; 2 years ago

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#6

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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