Re: Change of function in an ODE

*To*: mathgroup at smc.vnet.net*Subject*: [mg109091] Re: Change of function in an ODE*From*: Simon Pearce <Simon.Pearce at nottingham.ac.uk>*Date*: Mon, 12 Apr 2010 23:00:15 -0400 (EDT)

I would use: eqn == r^4 R''''[r] + 2 r^3 R'''[r] - r^2 R''[r] + r R'[r] - L^4 r^4 R[r]; Simplify[eqn /. R -> Function[{r}, r^2 Log[r] G[r]]] Which works well for me. Simon -----Original Message----- From: Sam Takoy [mailto:sam.takoy at yahoo.com] Sent: 11 April 2010 09:33 To: mathgroup at smc.vnet.net Subject: [mg109091] [mg109043] Change of function in an ODE Hi, I'm solving DSolve[r^4 R''''[r] + 2 r^3 R'''[r] - r^2 R''[r] + r R'[r] - L^4 r^4 R[r] ==== 0, R[r], r] // Simplify Now, I would like to make the substitution R[r]==r^2 Log[r] G[r], formulate the equation for G[r] and solve it. What's the proper syntax for that? Thanks, Sam