题目内容
(2013•江阳区模拟)先找规律,再填数:
+
-1=
,
+
-
=
,
+
-
=
,
+
-
=
,…,
+
-
?
?=
.
| 1 |
| 1 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 2 |
| 1 |
| 12 |
| 1 |
| 5 |
| 1 |
| 6 |
| 1 |
| 3 |
| 1 |
| 30 |
| 1 |
| 7 |
| 1 |
| 8 |
| 1 |
| 4 |
| 1 |
| 56 |
| 1 |
| 2013 |
| 1 |
| 2014 |
| 1 |
| 1007 |
| 1 |
| 1007 |
| 1 |
| ( )×2014 |
分析:观察不难发现,两个连续自然数的倒数的和减去后一个自然数的一半的倒数,等于这两个自然数的乘积的倒数.
解答:解:∵
+
-1=
,2=1×2,
+
-
=
,12=3×4,
+
-
=
,30=5×6,
+
-
=
,56=7×8,
…,
∴
+
-
=
.
故答案为:
,2013.
| 1 |
| 1 |
| 1 |
| 2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| 2 |
| 1 |
| 12 |
| 1 |
| 5 |
| 1 |
| 6 |
| 1 |
| 3 |
| 1 |
| 30 |
| 1 |
| 7 |
| 1 |
| 8 |
| 1 |
| 4 |
| 1 |
| 56 |
…,
∴
| 1 |
| 2013 |
| 1 |
| 2014 |
| 1 |
| 1007 |
| 1 |
| 2013×2014 |
故答案为:
| 1 |
| 1007 |
点评:本题是对数字变化规律的考查,比较简单,仔细观察分母的变化找出规律是解题的关键.
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