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I don't think that is what I need, as my values for n, k, j are always unknown (and thus not set) anyway. I was searching for a way to somehow tell Mathematica it should regard u[n,k,j] as known and u[n,k,j-1] etc. as unknown and then give me an...
Then what would be the right way of telling Mathematica what I want? I tried to input my equations e.g. like this eqn={D[u[x,y],x]+D[v[x,y],y]==0,eta[x,y]==Sqrt[ue/(nu*x)]*y,psi==Sqrt[ue*nu*x]*f ...