Nuprl Lemma : rng_sum_plus 11,40

r:Rng, ab:.
(a  b)
 (EF:({a..b}|r|).
 ((ra  i < bE(i) +r F(i)) = (((ra  i < bE(i)) +r ((ra  i < bF(i)))  |r|) 
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DefinitionsIMonoid, t  T, IAbMonoid, x:AB(x), t.2, t.1, , P & Q, Mon, Group{i}, AbGrp, r+gp, *, |g|, (ri  k < jE(k)
Lemmasrng wf, abgrp wf, comm wf, grp id wf, grp op wf, grp car wf, monoid p wf, add grp of rng wf b, mon itop op

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