问题 填空题
lim
n→∞
1
n2
(1+
3
2
+2+…+
n+1
2
)
=______.
答案

根据等差数列求和公式,得

1+

3
2
+2+…+
n+1
2
=
1
2
•n•(1+
n+1
2
)=
n(n+3)
4

lim
n→∞
1
n2
(1+
3
2
+2+…+
n+1
2
)=
lim
n→∞
(
1
n2
n2+3n
4
)
=
lim
n→∞
n+3
4n
=
1
4

故答案为:

1
4

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