A = 3/1.2 + 3/2.3 + 3/3.4 + . . .+ 3/2017.2018 .Tim tong cua day so A
B=5/2.5 + 5/5.8 + . . .+5/299.302 .Tim tong day so B
C = 2/1.7 + 2/7.13 + . . .+2/601.607 .Tim tong day so C
D = 1/1.3 + 1/3.5 + . . .+1/(2n + 1)(2n + 3) .Tim day so D
CAC BAN GIUP MINH VOI . CAC BAN GIUP MINH MINH TICK CHO NHE