theorem
 for f,g being A-defined Function, h being Function
  holds h+*f, h+*g equal_outside A
proof
 let f,g be A-defined Function, h be Function;
   h, h+*f equal_outside A by Th129;
   then
A1: h+*f,h equal_outside A;
   h, h+*g equal_outside A by Th129;
 hence thesis by A1;
end;
