题目内容
计算下面各题.
|
|
| ||||||||||||||||||
1-(
|
|
|
分析:(1)(2)(3)先找出三个分母的最小公倍数做公分母,再根据分数的性质把分数通分成同分母分数,进而分母不变,把分子相加减;
(4)(5)(5)要先算括号里面的,在算括号外面的.
(4)(5)(5)要先算括号里面的,在算括号外面的.
解答:解:(1)
+
-
=
+
-
=
=
;
(2)
-
+
=
-
+
=
;
(3)
+
-
=
+
-
=
=
;
(4)1-(
-
)
=1-(
-
)
=1-
=
;
(5)
+(
-
)
=
+(
-
)
=
+
=
;
(6)
-(
+
)
=
-(
+
)
=
-
=
=
.
3 |
10 |
1 |
6 |
2 |
5 |
=
9 |
30 |
5 |
30 |
12 |
30 |
=
2 |
30 |
=
1 |
15 |
(2)
7 |
8 |
1 |
2 |
3 |
4 |
=
7 |
8 |
4 |
8 |
6 |
8 |
=
9 |
8 |
(3)
1 |
2 |
3 |
5 |
7 |
10 |
=
5 |
10 |
6 |
10 |
7 |
10 |
=
4 |
10 |
=
2 |
5 |
(4)1-(
3 |
4 |
2 |
5 |
=1-(
15 |
20 |
8 |
20 |
=1-
7 |
20 |
=
13 |
20 |
(5)
1 |
3 |
5 |
6 |
3 |
4 |
=
1 |
3 |
10 |
12 |
9 |
12 |
=
4 |
12 |
1 |
12 |
=
5 |
12 |
(6)
4 |
5 |
1 |
6 |
3 |
10 |
=
4 |
5 |
5 |
30 |
9 |
30 |
=
24 |
30 |
14 |
30 |
=
10 |
30 |
=
1 |
3 |
点评:此题考查异分母分数加减法的混合运算:有括号时,要先算括号里面的,再算括号外面的;没有括号时,要先通分,再计算.
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