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hugle/sumexpand.nb

Last active April 17, 2022 19:16
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Expand summation expression and apply the distribution law
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sumexpand.nb
SumExpand[exp_] :=
exp /. Sum[c_, {i_, a_, b_}] :>
Distribute[Sum[ExpandAll[c], {i, a, b}]];
rule = Sum[Times[Longest[u___], x___], {y_, z___}] :>
Times[u] Sum[Times[x], {y, z}] /; (FreeQ[{u}, y]);
SumSimplify[exp_] := SumExpand[exp] /. rule
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