Ta có :A=3/4+8/9+15/16+...+9999/10000
=>A=(1-1/4)+(1-1/9)+(1-1/16)+...+(1-/10000)
=>A=(1-1/2^2)+(1-1/3^2)+(1-1/4^2)+...+(1-1/100^2)
=>A=(1+1+1+....+1)-(1/2^2+1/3^2+1/4^2+...+1/100^2)
=>A=99-(1/2^2+1/3^2+1/4^2+...+1/100^2)<99
=>A<99(1)
Ta có B=1/2^2+1/3^2+1/4^2+...+1/100^2
=>B<1/1.2+1/2.3+1/3.4+...+1/99.100
=>B<1/1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100
=>B<1-1/100
=>A>99-(1-1/100)
=>A>99-1+1/100
=>A>98+1/100>98
=>A>98(2)
Từ (1),(2)=>99>AA>98
=>Chọn ý C nhoa
