You are Here: Home >< Maths

# AQA FP3 Differential equations watch

1. I've no idea where to start on question 6b and question 7. I don't think I even know what they're asking.
Attached Files
2. Doc1.doc (268.5 KB, 55 views)
3. (Original post by maggiehodgson)
I've no idea where to start on question 6b and question 7. I don't think I even know what they're asking.
For 6(b) you are simply required to show that satisfies the d.e.
so put find substirute into the left hand side of the d,e, and show that it equals 0.
4. (Original post by brianeverit)
For 6(b) you are simply required to show that satisfies the d.e.
so put find substirute into the left hand side of the d,e, and show that it equals 0.
Thanks. I thought I would have had to start from the DE end and work towards the y=...

This help might move me forward for question 7 now. Thank you.
5. (Original post by brianeverit)
For 6(b) you are simply required to show that satisfies the d.e.
so put find substirute into the left hand side of the d,e, and show that it equals 0.
I'm afraid that question 6 has not helped with question 7. I'm using the AQA FP3 booklet from their website. On page 105 it goes into deriving the different form of solution. Would I have to do that or can you think of a simpler method?

I'm attaching the start of the AQA booklet page to show you what I'm talking about.

Thanks
Attached Files
6. Doc1.doc (268.5 KB, 36 views)
7. (Original post by maggiehodgson)
I'm afraid that question 6 has not helped with question 7. I'm using the AQA FP3 booklet from their website. On page 105 it goes into deriving the different form of solution. Would I have to do that or can you think of a simpler method?

I'm attaching the start of the AQA booklet page to show you what I'm talking about.

Thanks

Get the second derivative in the bsame way and sub into the d,e,. Then use the fact that you know
and
8. (Original post by brianeverit)

Get the second derivative in the bsame way and sub into the d,e,. Then use the fact that you know
and

Is this it?
Attached Images
9. Scan0002.pdf (353.7 KB, 41 views)
10. (Original post by maggiehodgson)
Is this it?
Yes. To complte it just take out the factors of A and B and observe that the contents of the brackets are zero since y1 and y2 are solutions of the d.e.
11. (Original post by brianeverit)
Yes. To complte it just take out the factors of A and B and observe that the contents of the brackets are zero since y1 and y2 are solutions of the d.e.

Many thanks. I think it's beginning to make sense but, for some reason, I feel that I should have to work towards y = Ay1 + By2 rather than starting from there and showing that it works.
12. (Original post by maggiehodgson)
Many thanks. I think it's beginning to make sense but, for some reason, I feel that I should have to work towards y = Ay1 + By2 rather than starting from there and showing that it works.
Definitely not. The method I have suggested is the standard method.
Google "Differentialm equations, linear combination of solutions" and look at some of the articles.
13. (Original post by brianeverit)
Definitely not. The method I have suggested is the standard method.
Google "Differentialm equations, linear combination of solutions" and look at some of the articles.
Oh no, I believe you. It's me just thinking the wrong way.

Thanks for all you help over this and several other questions in the past. It's very much appreciated.

Happy New Year
14. (Original post by maggiehodgson)
Oh no, I believe you. It's me just thinking the wrong way.

Thanks for all you help over this and several other questions in the past. It's very much appreciated.

Happy New Year
Same to you and I'm just pleased to be able to help.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 1, 2015
Today on TSR

### The most controversial member on TSR?

Who do you think it is...

### Is confrontation required?

Discussions on TSR

• Latest
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE