问题 解答题
用递等式计算,能简算的要简算.
3
8
+
7
12
-
5
16
23
12
-(
1
8
+
5
6
7
9
+
23
10
-(
13
10
+
2
9
3
4
-
2
7
+(
1
4
+
2
7
)+
3
8
答案

(1)

3
8
+
7
12
-
5
16

=

23
24
-
5
16

=

31
48

(2)

23
12
-(
1
8
+
5
6
),

=

23
12
-
23
24

=

23
24

(3)

7
9
+
23
10
-(
13
10
+
2
9
),

=

7
9
+
23
10
-
13
10
-
2
9

=(

7
9
-
2
9
)+(
23
10
-
13
10
),

=

5
9
+1,

=1

5
9

(4)

3
4
-
2
7
+(
1
4
+
2
7
)+
3
8

=(

3
4
+
1
4
)+(
2
7
-
2
7
)+
3
8

=1+

3
8

=1

3
8

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