Re: Sum simplifying

*To*: mathgroup at smc.vnet.net*Subject*: [mg89223] Re: [mg89200] Sum simplifying*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Fri, 30 May 2008 02:55:29 -0400 (EDT)*Reply-to*: hanlonr at cox.net

sub = (Sum[a_. * x_ + y_., {k_, lower_, upper_}] /; FreeQ[a, k]) :> a*Sum[x, {k, lower, upper}] + Sum[y, {k, lower, upper}]; expr = Sum[a[k]*I + b[k], {k, 1, n}] - I*Sum[a[k], {k, 1, n}] - Sum[b[k], {k, 1, n}]; expr /. sub 0 Bob Hanlon ---- Lari <lari.jarvenpaa at luukku.com> wrote: > Hey, > > I'd like to simplify a following type of sum: > > In[62]:= Sum[a[k]*I + b[k], {k, 1, n}] - I*Sum[a[k], {k, 1, n}] - > Sum[b[k], {k, 1, n}] > > In[63]:= FullSimplify[%] > > The result should obviously be zero; however, Mathematica returns the same expression. If I put n an integer value it knows how to simplify. How do I make it understand that also with a symbolic upper limit? > > Hope someone can help! > > Thanks, > Lari >