题目内容
先阅读,再解题:
因为1-
=
,
-
=
,
-
=
,…
所以
+
+
+…+
=(1-
)+(
-
)+(
-
)+…+(
-
)=1-
+
-
+
-
+…+
-
=1-
=
参照上述解法计算:
+
+
+…+
.
因为1-
| 1 |
| 2 |
| 1 |
| 1×2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 2×3 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 3×4 |
所以
| 1 |
| 1×2 |
| 1 |
| 2×3 |
| 1 |
| 3×4 |
| 1 |
| 49×50 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 49 |
| 1 |
| 50 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 49 |
| 1 |
| 50 |
| 1 |
| 50 |
| 49 |
| 50 |
参照上述解法计算:
| 1 |
| 1×3 |
| 1 |
| 3×5 |
| 1 |
| 5×7 |
| 1 |
| 49×51 |
原式=
(1-
+
-
+
-
+…+
-
)=
(1-
)=
×
=
.
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| 1 |
| 5 |
| 1 |
| 5 |
| 1 |
| 7 |
| 1 |
| 49 |
| 1 |
| 51 |
| 1 |
| 2 |
| 1 |
| 51 |
| 1 |
| 2 |
| 50 |
| 51 |
| 25 |
| 51 |
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