题目内容
简便计算：
+
+
+
+
．
| 1 |
| 20 |
| 1 |
| 30 |
| 1 |
| 42 |
| 1 |
| 56 |
| 1 |
| 72 |
考点：分数的简便计算
专题：运算定律及简算
分析：
=
-
，
=
-
，
=
-
，
=
-
，
=
-
，然后再进一步计算．
| 1 |
| 20 |
| 1 |
| 4 |
| 1 |
| 5 |
| 1 |
| 30 |
| 1 |
| 5 |
| 1 |
| 6 |
| 1 |
| 42 |
| 1 |
| 6 |
| 1 |
| 7 |
| 1 |
| 56 |
| 1 |
| 7 |
| 1 |
| 8 |
| 1 |
| 72 |
| 1 |
| 8 |
| 1 |
| 9 |
解答：
解：
+
+
+
+
=（
-
）+（
-
）+（
-
）+（
-
）+（
-
）
=
-
+
-
+
-
+
-
+
-
=
-
=
．
| 1 |
| 20 |
| 1 |
| 30 |
| 1 |
| 42 |
| 1 |
| 56 |
| 1 |
| 72 |
=（
| 1 |
| 4 |
| 1 |
| 5 |
| 1 |
| 5 |
| 1 |
| 6 |
| 1 |
| 6 |
| 1 |
| 7 |
| 1 |
| 7 |
| 1 |
| 8 |
| 1 |
| 8 |
| 1 |
| 9 |
=
| 1 |
| 4 |
| 1 |
| 5 |
| 1 |
| 5 |
| 1 |
| 6 |
| 1 |
| 6 |
| 1 |
| 7 |
| 1 |
| 7 |
| 1 |
| 8 |
| 1 |
| 8 |
| 1 |
| 9 |
=
| 1 |
| 4 |
| 1 |
| 9 |
=
| 5 |
| 36 |
点评：考查了分数的拆项，然后再进一步解答．
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