Bug in RSolve?

*To*: mathgroup at smc.vnet.net*Subject*: [mg18897] Bug in RSolve?*From*: "Hossein Kazemi" <kazemi at som.umass.edu>*Date*: Mon, 26 Jul 1999 14:27:43 -0400*Organization*: University of Massachusetts, Amherst*Sender*: owner-wri-mathgroup at wolfram.com

Is this a bug in RSolve (Version 4.0)? In[1]:= << DiscreteMath`RSolve` In[2]:= RSolve[x[n] == 3 + 4 u[n], x[n], n]; In[3]:= x[n_] = x[n] /. %[[1]]; In[4]:= x[1] Out[4]= 3 - 4 u[-1] + 4 u[1] What does u[-1] doing here? In[5]:= x[2] Out[5]= 3 - 4 u[-1] + 4 u[2] What does u[-1] doing here? In[6]:= u[n_] := n In[7]:= x[2] Out[7]= 15 This does not make any sense at all. Clearly, x[2]= 3 + 4*2 = 11