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Re: is it a bug?!please help.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg107252] Re: is it a bug?!please help.
  • From: "Nasser M. Abbasi" <nma at 12000.org>
  • Date: Sun, 7 Feb 2010 06:10:50 -0500 (EST)
  • References: <hkgl3d$6t8$1@smc.vnet.net>

"olfa" <olfa.mraihi at yahoo.fr> wrote in message 
news:hkgl3d$6t8$1 at smc.vnet.net...
> Hello mathematica community,
> for Sum[k[i], {i, 1, n}] + Sum[k[i], {i, n + 1, m}]
> why mathematica cannot give as output Sum[k[i],{i,1,m]]?!
> please help.
>

My guess is that "+" is currently not defined for Sum while it is in its 
symbolic form?

But it works ok when one plugs in some actual integer values for n and m:

Clear[s1,s2,k,n,m,i]
s1=Sum[k[i],{i,1,n}]
s2=Sum[k[i],{i,n+1,m}]

s1+s2/.{n->5,m->7}

k[1]+k[2]+k[3]+k[4]+k[5]+k[6]+k[7]


--Nasser







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