You are Here: Home >< Maths

# Differential Equation HELP please Watch

1. du/dt = au(b-u).

By separating variables and using partial fractions show that

ln (u/(b-u)) = abt + C

If the solution didnt have the b on the RHS i would be okay, but I cannot see how to do this with the b on the RHS. Any help appreciated.

Zezzy
2. Use partial fractions
3. (Original post by Serano)
Use partial fractions
How on this question?
4. show your working so far...
and yeh doing some re-arranging in my head, i'd probably use partial fractions too
5. (Original post by didgeridoo12uk)
du/dt = au(b-u)

du/ u(b-u) = a dt

but I know I need something like 1/u + 1/(b-u) = ab dt to get the answer :/
6. (Original post by Zezzy)
du/dt = au(b-u)

du/ u(b-u) = a dt

but I know I need something like 1/u + 1/(b-u) = ab dt to get the answer :/
dont worry about trying to get the answer they've given you. just throw maths at it and worry about that when you've finished.

so obviously not you need to do some partial fractions on 1/(u(b-u)) to split it up...
7. (Original post by didgeridoo12uk)
dont worry about trying to get the answer they've given you. just throw maths at it and worry about that when you've finished.

so obviously not you need to do some partial fractions on 1/(u(b-u)) to split it up...
So like D/u + E/(b-u) = 1

D(b-u) + E(u) = 1

then what?
8. (Original post by Zezzy)
So like D/u + E/(b-u) = 1

D(b-u) + E(u) = 1

then what?
substitue values in for u that will let you work out the values of D and E by eliminating either D or E.

for example u = b
9. I have it! Thanks very much

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: November 27, 2010
Today on TSR

### Degrees to get rich!

... and the ones that won't

### Cambridge interviews pour in...

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

### 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
• ## 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.