问题
选择题
数列{an}的前n项和为Sn,若an=
|
答案
∵an=
=1 n(n+2)
(1 2
-1 n
)1 n+2
∴S10=
(1-1 2
+1 3
-1 2
+…+1 4
-1 9
+1 11
-1 10
)1 12
=
(1+1 2
-1 2
-1 11
)=1 12 175 264
故选A
数列{an}的前n项和为Sn,若an=
|
∵an=
=1 n(n+2)
(1 2
-1 n
)1 n+2
∴S10=
(1-1 2
+1 3
-1 2
+…+1 4
-1 9
+1 11
-1 10
)1 12
=
(1+1 2
-1 2
-1 11
)=1 12 175 264
故选A