Re: simplification rule for infinite sum
- To: mathgroup at smc.vnet.net
- Subject: [mg105813] Re: [mg105799] simplification rule for infinite sum
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Sun, 20 Dec 2009 06:53:58 -0500 (EST)
- Reply-to: hanlonr at cox.net
expr = a Sum[(n + 2) c[n] x^n, {n, 5, Infinity}] + b Sum[(n + 2) (n + 1) c[n] x^n, {n, 5, Infinity}]; expr /. c1_*Sum[expr1_, iter_List] + c2_*Sum[expr2_, iter_List] :> Sum[Simplify[c1*expr1 + c2*expr2], iter] Sum[(n + 2)*c[n]*x^n*(a + b*n + b), {n, 5, Infinity}] Bob Hanlon ---- "Ruth Lazkoz S=C3=A1ez" <ruth.lazkoz at ehu.es> wrote: ============= Hi, I have managed to define rules with patterns to shift indexes on the coefficients of infinite sums, but I have failed to do something so apparently simple as making Mathematica understand that this a Sum[(n + 2) c[n] x^n, {n, 5, Infinity}] + b Sum[(n + 2) (n + 1) c[n] x^n, {n, 5, Infinity}] should be simplified to this Sum[(n + 2) (a + b (n + 1)) c[n] x^n, {n, 5, Infinity}] Can someone help me? Thanks a lot, Ruth Lazkoz