You are Here: Home >< Maths

# Differential Equation Watch

1. I need to find the general solution in implicit form, of this equation:

Ive then got:

But dont know where to go next?
2. It's not separable, so there's no use multiplying through by the denominator (at least not yet).

Notice that you can write it as , which indicates that the substitution may prove to be useful.
3. From the offset, try making a substituting that involves both x and y (motivation: "implicit". And it looks like it'll make things nicer).
4. (Original post by bikinmad)
I need to find the general solution in implicit form, of this equation:

Ive then got:

But dont know where to go next?
Possibly the substitution z = x + y
5. so i let u = x + y

And i got up to the point:

Is this correct so far?
6. (Original post by bikinmad)
so i let u = x + y

And i got up to the point:

Is this correct so far?
It's correct, but there's no need for the last step. Your aim is to separate the variables - so put du/dx on one side, everything else on the other and use separation of variables (you'll want to simplify a bit before dividing across)
7. (Original post by bikinmad)
so i let u = x + y

And i got up to the point:

Is this correct so far?
Yup, although what I'd recommend doing is combining the fraction and the 1 into a single fraction. Then you can separate things.

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: December 15, 2010
Today on TSR

### Oxford interview invitations

When can you expect yours?

### Official Cambridge interview invite list

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

## Make your revision easier

### 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

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.