same input ... different results???

*To*: mathgroup at smc.vnet.net*Subject*: [mg87246] same input ... different results???*From*: ich <dotwin at gmx.ch>*Date*: Sat, 5 Apr 2008 04:23:48 -0500 (EST)

hi, i'm trying to solve the following equation with mathematica. why are there different results depending on whether or not i factor x out (see the two def. for f1)? Sum[f1[n1, n2, x, m, i, j, k], {i, 0, n1}, {j, 0, n2}, {k, 0, n2 + i - j}] f1[n1_, n2_, x_, m_, i_, j_, k_] := Exp[I*2*Pi*(m/3*(n1 + n2 - i - 2 j - k) + x*(n2 + i - j - 2 k))] f1[n1_, n2_, x_, m_, i_, j_, k_] := Exp[I*2*Pi*(m/3*(n1 + n2 - i - 2 j - k) + x*n2 + x*i - x*j - 2 x*k)] and still, both results do not match the sum if i enter specific values. so there must be something wrong, but what? thx in advance.