... xoa(DaThuc &A,int vt); void rutgon(DaThuc &A); DaThuc Doi(DaThuc A); DaThuc Tong(DaThuc A,DaThuc B); DaThuc Hieu(DaThuc A,DaThuc B); DaThuc Tich(DaThuc dt1,DaThuc dt2); DaThuc Thuong(DaThuc bichia,DaThuc ... bichia,DaThuc chia); main() { DaThuc A,B ,C, D,E,F; cout...