题目内容
用递等式计算.
(1)
-
+
(2)1-
+
(3)
+
-
.
(1)
| 12 |
| 16 |
| 8 |
| 16 |
| 4 |
| 16 |
(2)1-
| 7 |
| 8 |
| 1 |
| 8 |
(3)
| 9 |
| 20 |
| 2 |
| 20 |
| 11 |
| 20 |
分析:根据同分母分数加减法的计算方法进行计算.
解答:解:(1)
-
+
,
=
+
,
=
;
(2)1-
+
,
=
+
,
=
;
(3)
+
-
,
=
-
,
=0.
| 12 |
| 16 |
| 8 |
| 16 |
| 4 |
| 16 |
=
| 4 |
| 16 |
| 4 |
| 16 |
=
| 1 |
| 2 |
(2)1-
| 7 |
| 8 |
| 1 |
| 8 |
=
| 1 |
| 8 |
| 1 |
| 8 |
=
| 1 |
| 4 |
(3)
| 9 |
| 20 |
| 2 |
| 20 |
| 11 |
| 20 |
=
| 11 |
| 20 |
| 11 |
| 20 |
=0.
点评:同分母分数相加减,分母不变,只把分子相加减.
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