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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