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Question: Weird behavior of subs and isolate in PDE systems

Question:Weird behavior of subs and isolate in PDE systems

Sergio Parreiras 135 Maple
October 23 2013
0

Hi folks, I'm running Maple 17.02 and getting very different behaviors from subs and isolate. My actual expressions are way more complicated but this simple example illustrates the problem:

restart; with(PDEtools); F := diff_table(f(x, y, w, z, a, b));

subs(F[x] = Z(x, y, w, z, a, b), F[x]+F[x, b]-10);

subs(F[x] = Z(x, y, w, z, a, b), F[x]+F[x, y]-10);

The last line gives me what I want  Z+Z[y]-10 but the second line gives me Z+F[x,b]-10. That is, if I use b instead of y as variable, subs ignores the second derivative...

Can any one replicate this behavior? Is it a bug? Thanks for any help.
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