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MathGroup Archive 2005

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Re: Problem with DSolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53525] Re: Problem with DSolve
  • From: "Scout" <user at domain.com>
  • Date: Sat, 15 Jan 2005 21:07:55 -0500 (EST)
  • References: <csaek2$oss$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

from "Anand"
> Consider this simple 1st order equation
>
> DSolve[(y'[x])^2 - x y'[x] + y[x] == 0, y[x], x]
>
> The generic solution should be y= c ( x - c)
> and in addition a singular solution of this equation is y = x2/4 .
>
> The solution Mathematica produces is different. At least I could not
> relate it to the above solutions. What am I missing?
> sincerely, -anand.
>
>
Hi!
Well, the solution of the diff. equation produced by Math. is
          Out[1]    y[x]=-1/4 c (2x + c).
Rename the constant c with another constant to get your own solution:
           %1 /. c-> -2 b
and finally: y[x]= b (x-b).
 The Cs constants  in the diff. solutions are "arbitrary".

~ Scout ~

 


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