问题 解答题
用递等式计算,能简便的要简便.
2
5
+
2
9
+
7
9
+
4
5

2
8
11
-(
8
11
-
2
5
9
8
+
1
8
-
6
7
-
1
7
1
2
+
2
3
+
3
5
37
16
-
13
17
-
17
16
-
4
17
3
8
+
3
4
-
3
8
+
3
4
答案

2
5
+
2
9
+
7
9
+
4
5

=(

2
5
+
4
5
)+(
2
9
+
7
9

=1

1
5
+1

=2

1
5

2

8
11
-(
8
11
-
2
5

=2

8
11
-
8
11
+
2
5

=2+

2
5

=2

2
5

9
8
+
1
8
-
6
7
-
1
7

=(

9
8
+
1
8
)-(
6
7
+
1
7

=1

1
4
-1

=

1
4

1
2
+
2
3
+
3
5

=1

1
6
+
3
5

=1

23
30

37
16
-
13
17
-
17
16
-
4
17

=(

37
16
-
17
16
)-(
13
17
+
4
17

=

20
16
-1

=

1
4

3
8
+
3
4
-
3
8
+
3
4

=(

3
8
-
3
8
)+(
3
4
+
3
4

=1

1
2

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