Tính: E = 1/99 - 1/99.98 - 1/98.97 - ... - 1/3.2 - 1/2.1

E=1/99 -1/99.98-1/98.97-...-1/3.2-1/2.1

B=1/99-(1/99.97+1/97.95+...+1/3.1