theorem
  R1 - R2 = (i|->0.K) implies R1 = R2
proof
  assume R1 - R2 = (i|->0.K);
  then R1 + - R2 = (i|->0.K) by FINSEQOP:84;
  then R1 = --R2 by Th27;
  hence thesis by Th28;
end;
