H
hoaseru


bai tap
1.cho tổng n so hang dau tien cua day~ so Sn=2n^2 +3n , n thuoc N*. chung minh rang day~ so Un la csc. tim so hang tong quat.
1.cho tổng n so hang dau tien cua day~ so Sn=2n^2 +3n , n thuoc N*. chung minh rang day~ so Un la csc. tim so hang tong quat.