Tínha) 1/1.2 + 1/2.3 + 1/3.4 +..........+ 1/8.9 + 1/9.10b) 1/3.4 + 1/4.5 + 1/5.6 + ...........+ 1/98.99 + 1/99.100
Đăng ký qua Google:
