递等式计算(能简便计算用简便计算): 4-917-817= 913-(913-211)= 30.8÷[14-(9.85+1.07)]=

递等式计算(能简便计算用简便计算): 4-917-817= 913-(913-211)= 30.8÷[14-(9.85+1.07)]= 56+38-18=

(1)4-
9
17
-
8
17

=4-(
9
17
+
8
17
),
=4-1,
=3;

(2)
9
13
-(
9
13
-
2
11
),
=
9
13
-
9
13
+
2
11

=
2
11


(3)30.8÷[14-(9.85+1.07)],
=30.8÷[14-10.92],
=30.8÷3.08,
=10;

(4)
5
6
+
3
8
-
1
8

=
5
6
+(
3
8
-
1
8
),
=
5
6
+
1
4

=
13
12
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