I'm using version 10.3 on Windows XP. The problem is solved with LinearAlgebra. > eqns := {a(s,y,z,t)+2*b(s,y,z,t)=0,3*a(s,y,z,t)-5*b(s,y,z,t)=0}; LinearAlgebra:-GenerateMatrix( eqns, [a(s,y,z,t),b(s,y,z,t)], augmented ); It's so strange how maple doesn't return the good answer for some computation. Thank you for your help.

May be, I wasn't clear. What I entered, was exactly what you have written higher and maple returns > eqns:= {a(s,y,z,t)+2*b(s,y,z,t)=0,3*a(s,y,z,t)-5*b(s,y,z,t)=0}: > linalg[genmatrix](eqns,[a(s,y,z,t),b(s,y,z,t)]); Error, (in linalg:-genmatrix) equations are not linear

Yes, that's exactly what I've.

U(s) is a little complicated; U(s):= k_1*(s-1)/(s+1)+k_2*((s-1)/(s+1)*ln(s)-4/(s+1)); so you can imagine the diffculty for Maple to solve with more complicated coeffs, then I guess resolving the system as I rewrite it returns to same if I solve it with no substitution. If solutions aren't good, I could see this when I replace coeffs by their effective expression. Isn't?

Thank you JacquesC, I solved the problem. My goal is to simplify the PDEs System that I got and then solve the system. I hoped that it'll be more easier for Maple but after one hour of computation, Maple was unable to find sol. If you have any proposition that could help maple to solve it, welcome. Sorry for my bad English. View 4780_beny1.mw on MapleNet or Download 4780_beny1.mw
View file details