
theorem XLMOD04:
  for k,m be Nat st m <> 0 holds (k-m) div m = (k div m)-1
proof
  let k,m be Nat;
  assume
AS: m <> 0;
  thus (k-m) div m = (k+m*(-1)) div m
    .= (k div m)+-1 by AS,NAT_D:61
    .= (k div m)-1;
end;
