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MathGroup Archive 2005

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Re: is this solvable?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56625] Re: is this solvable?
  • From: ames kin <ames_kin at yahoo.com>
  • Date: Sat, 30 Apr 2005 01:28:17 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Thanks to all those who have replied. 
 
a'[t] + b'[t] == -p1 a[t] - p2 b[t]
 
is a result of operating on two odes that have 3 variables. 
 
{
a'[t] == -p1 a[t] - p3 c[t]
b'[t] == p3 c[t] - p2 b[t]
}
 
adding the two equations allows me to get rid of p3 c[t] terms. ( Above system comes from a piece wise defined ODE system after a certain time point.)
 
but the problem was that I end up with the a'[t]+ b'[t] 
 
dan's suggestion of setting b[t]-> b0 allows a particular form of solutions to be found using the normal DSolve syntax. 
 
 

Don Taylor <dont at agora.rdrop.com> wrote:
In comp.soft-sys.math.mathematica you write:
>a'[t] + b'[t]== -p1 a[t] - p2 b[t]

>where {a[0]== a0, b[0]== b0}

>is this solvable in Mathematica? If so, how will I go about doing so?

>let's assume a[0]== a0, and b[0]==b0

>if symbolic solution isn't possible, then intial conditions of
>a[0]== 1, and b[0]==0.5 couild be used...(or any other numbers for that
>matter)

>thanks in advance.

Can you give me a bit more information about your problem?
I don't think I understand enough about what you are doing
to try to offer ideas.

Thank you


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