A
acteyro123


A=10. (1/1.2 + 5/2.3...............+ 89/9.10)
Moi moi nguoi giai dum minh bai nay,tks moi nguoi nhieu =((=((=((=((=((=((
Moi moi nguoi giai dum minh bai nay,tks moi nguoi nhieu =((=((=((=((=((=((