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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.


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