theorem
  for F being add-associative right_zeroed right_complementable non
  empty addLoopStr, a, b being Element of F holds a + b = -(-b + -a)
proof
  let F be add-associative right_zeroed right_complementable non empty
  addLoopStr, a,b be Element of F;
  thus a + b = --(a + b) by RLVECT_1:17
    .= -(-b + -a) by RLVECT_1:31;
end;
