# MEI C4 Qs 7i)Watch

#1
I Just don't understand the mark scheme!

http://www.mei.org.uk/files/papers/c410ja_4754.pdf

Thx
0
7 years ago
#2
You need to take the equation given, and calculate dx/dt and x(1-x) to check if they give the same answer, as well as checking the initial conditions.

The easiest way of doing it is to calculate (1-x) in terms of t by adding fractions, then work out x(1-x). Then calculate dx/dt using the chain rule.
0
#3
(Original post by ttoby)
You need to take the equation given, and calculate dx/dt and x(1-x) to check if they give the same answer, as well as checking the initial conditions.

The easiest way of doing it is to calculate (1-x) in terms of t by adding fractions, then work out x(1-x). Then calculate dx/dt using the chain rule.
How? ... What fractions?
0
7 years ago
#4
(Original post by Newyork Nagaram...)
How? ... What fractions?
.
0
7 years ago
#5
what you do now is put that solution x=1/(1+e^-t) into the right hand side of dx/dt=x(1-x)

if you then show that the right hand side you obtained by putting x into the equation is the same as just differentiating the x solution you were given, then the left hand side and right hand side are equal so the solution x=1/(1+e^-t) satisfies the differential equation.

lol neg
1
#6
(Original post by Farhan.Hanif93)
.
This is the Bit i don't Get... How is 1-x= 1-(1/1+e^-t)??
0
7 years ago
#7
(Original post by Newyork Nagaram...)
This is the Bit i don't Get... How is 1-x= 1-(1/1+e^-t)??
You're told to verify that the differential equation is satisfied by so you're gonna have to sub that in, in place of x, in the RHS and also calculate the derivative directly for the LHS and show that they are equal.
1
7 years ago
#8
(Original post by Newyork Nagaram...)
This is the Bit i don't Get... How is 1-x= 1-(1/1+e^-t)??
You're told that so
1
#9
Thank you everyone!!! I got IT !!! Rep+ Everyone!
0
X

new posts
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

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

### University open days

• Cranfield University
Cranfield Forensic MSc Programme Open Day Postgraduate
Thu, 25 Apr '19
• University of the Arts London
Open day: MA Footwear and MA Fashion Artefact Postgraduate
Thu, 25 Apr '19
• Cardiff Metropolitan University
Sat, 27 Apr '19

### Poll

Join the discussion

#### Have you registered to vote?

Yes! (443)
37.83%
No - but I will (88)
7.51%
No - I don't want to (80)
6.83%
No - I can't vote (<18, not in UK, etc) (560)
47.82%