题目内容
若数列{an}通项公式为an=
,则数列{an}的前5项和为______.
1 |
n(n+1) |
∵an=
=
-
,
∴a1+a2+…+a5
=(1-
)+(
-
)+…+(
-
)
=1-
=
.
故答案为:
.
1 |
n(n+1) |
1 |
n |
1 |
n+1 |
∴a1+a2+…+a5
=(1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
5 |
1 |
6 |
=1-
1 |
6 |
=
5 |
6 |
故答案为:
5 |
6 |
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