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Problems with DSolve

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  • Subject: [mg119654] Problems with DSolve
  • From: David King <drdavidbking at>
  • Date: Thu, 16 Jun 2011 04:01:05 -0400 (EDT)

Hello Mathematica Forum,

I am a new forum contributer, so it is nice to meet you.  I was hoping
at least one of you could help me out.  I am attempting to find an
exact solution to a system of differential equations

I  type in the following Dsolve  function:

 sol=DSolve[{x'[t] -(0.355+(0.645t/(t+223.06)))x[t]+0.311y[t]
+0.046z[t] - 0.149x[t] -0.259x[t],y'[t] 0.149x[t] -
0.311y[t],z'[t] 0.259x[t] -0.046z[t],x[0] D,y[0] 0,z[0] 0},

So far, Mathematica  returns the following:

Out[7]:=  DSolve[{x=A2[t] -0.408 x[t]+(-0.355-(0.645 t)/(223.06 +t)) x[t]
+0.311 y[t]+0.046 z[t],y=A2[t] 0.149 x[t]-0.311 y[t],z=A2[t] 0.259
x[t]-0.046 z[t],x[0] D,y[0] 0,z[0] 0},{x[t],y[t],z[t]},t]

Which is what my question is.... This is kind of like asking  "Who's on
first?"  and mathematica answers:  "Who's on first."  Which is what my
question is....  I am pretty sure that my syntax is correct.  Anyway,
I was hoping that you might be able to knock this one out of the

I have a numerical solution, just not an exact solution.

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