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Re: Manipulating differential equations



dg1 /. Thread[{#,D[#,x],D[#,x,x]} & /@ (c[x]->Exp[-a x])]

Hope that helps

Martin Heimann wrote:
> Dear colleagues,
> I would like to insert test functions into an expression that contains
> differentials:
> dg1 = c''[x] + g c'[x]
> I would like e.g. to replace c[x] by Exp[-a x]:
> dg1/.c[x]->Exp[-a x]
> but this doesn't work; one has to put substitution rules for each of the
> derivatives explicitly. Is there a more elegant way to achieve this?
> Cheers,
> Martin Heimann

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