Chuyên đề thực hiện phép tính bồi dưỡng học sinh giỏi Toán 6 - 7
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CHUYÊN ĐỀ : THỰC HIỆN PHÉP TÍNH
DẠNG 1: RÚT GỌN Bài 1: Thực hiện phép tính:
a,
12 5 6 2 10 3 5 2
2 6 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) (125.7) 5 .14 − − − +
b,
18 7 3 15 15
10 15 14 13 2 .18 .3 3 .2 2 .6 3 .15.4
+ +
c,
6 5 9
4 12 11 4 .9 6 .120 8 .3 6 +
−
HD :
a, Ta có:
12 5 6 2 10 3 5 2
2 6 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) (125.7) 5 .14 − − − +
( ) ( ) ( ) ( ) ( )
6 2 5 2 12 5 2 2 10 3 2 2
3 12 6 3 3 9 3 3 2 .3 2 . 3 5 .7 5 . 7
2 .3 5 .7 5 .2 .7
− − = −
+
( ) ( ) ( )
12 4 10 3 12 5 12 4 10 3 10 4
12 6 9 3 9 3 3 12 6 9 3 2 .3 3 1 5 .7 1 7 2 .3 2 .3 5 .7 5 .7 2 .3 5 .7 5 .2 .7 2 .3 5 .7 1 8 − − − − = − = − + + 2 2 5.6 28 3 9 9 − = − =
b, Ta có:
18 7 3 15 15
10 15 14 13 2 .18 .3 3 .2 2 .6 3 .15.4
+ +
18 7 14 3 15 15 25 17 15 15
10 15 15 14 28 25 15 15 28 2 .2 .3 .3 3 .2 2 .3 3 .2 2 .2 .3 3 .3.5.2 2 .3 3 .2 .5 + + = = + +
( ) ( )
( ) 15 15 10 2 10 2
10 25 15 3 2 .3 2 .3 1 2 .3 1
2 41 2 .3 1 2 .5
+ + = = +
c, Ta có:
6 5 9
4 12 11 4 .9 6 .120 8 .3 6 +
−
= ( ) ( )
( )
6 5 2 2 9 9 3 12 10 12 10
4 12 12 11 11 3 12 11 11 2 . 3 2 .3 .2 .3.5 2 .3 2 .3 .5 2 .3 2 .3 2 .3 2 .3
+ + = − −
( ) ( )
12 10
11 11 2 .3 1 5 2.6 4 2 .3 2.3 1 3.5 5 + = = = −
Bài 2: Thực hiện phép tính:
a,
15 9 20 9
9 16 29 6 5.4 .9 4.3 .8 5.2 .9 7.2 .27 − −
b,
4 2 2
3 3 2 2 .5 .11 .7 2 .5 .7 .11
c,
11 12 11 11
12 11 11 11 5 .7 5 .7 5 .7 9.5 .7 + +
HD :
a, Ta có:
15 9 20 9
29 16 29 6 5.4 .9 4.3 .8 5.2 .3 7.2 .27 − −
= ( ) ( )
29 18 2 30 18 29 20
29 16 29 18 29 16 2 2 .3 5.2 3 5.2 .3 2 .3 5.2 .3 7.2 .3 2 .3 5 7.3
− − = − −
=
23 9 58 58 − = −
b, Ta có:
4 2 2
3 3 2 2 .5 .11 .7 2 .5 .7 .11
= 2.11 22 5.7 35 =
c, Ta có:
11 12 11 11
12 11 11 11 5 .7 5 .7 5 .7 9.5 .7 + + = ( ) ( )
11 11
11 11 5 .7 7 1 8 4 5 .7 5 9 14 7 + = = +
Bài 3: Thực hiện phép tính:
a,
22 7 15
14 2 11.3 .3 9 (2.3 )
− b,
10 10 10 9
9 10 2 .3 2 .3 2 .3
− c,
5 4 9
10 8 8 4 .9 2.6 2 .3 6 .20 − +
HD :
a, Ta có:
22 7 15
14 2 11.3 .3 9 (2.3 )
− = ( ) 29 29 30
2 28 2 28 3 . 11 3 11.3 3 3.8 6 2 .3 2 .3 4 − − = = =
b, Ta có:
10 10 10 9
9 10 2 .3 2 .3 2 .3
− ( ) 10 9
9 10 2 .3 3 1 2.2 4 2 .3 3 3 − = = =
c, Ta có:
5 4 9
10 8 8 4 .9 2.6 2 .3 6 .20 − + ( ) ( )
10 8 10 8 10 9
10 8 10 8 10 8 2 .3 1 3 2 .3 2 .3 2 1 2 .3 2 .3 .5 2 .3 1 5 6 3 − − − − = = = = + +
Bài 4: Thực hiện phép tính:
a,
12 5 6 2 10 3 5 2
2 6 4 5 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) 8 .3 (125.7) 5 .14 − − − + + b,
15 9 20 9
9 19 29 6 5.4 .9 4.3 .8 5.2 .6 7.2 .27 − − c,
5 4 9
10 8 8 4 .9 2.6 2 .3 6 .20 − +
HD:
2
a, Ta có :
12 5 6 2 10 3 5 2
2 6 4 5 3 9 3 2 .3 4 .9 5 .7 25 .49 (2 .3) 8 .3 (125.7) 5 .14 − − − + +
= ( ) ( )
( ) ( )
( ) 12 4 10 3 12 5 12 4 10 3 10 4
12 6 12 5 9 3 9 3 3 12 5 9 3 2 .3 3 1 5 .7 1 7 5. 6 2 .3 2 .3 5 .7 5 .7 10 2 .3 2 .3 5 .7 5 .7 .2 2 .3 3 1 5 .7 1 8 9 3 − − − − − − − = − = = + + + +
b, Ta có :
15 9 20 9
9 19 29 6 5.4 .9 4.3 .8 5.2 .6 7.2 .27 − −
= ( ) ( )
29 18 2 30 18 20 29
28 19 29 18 28 18 2 .3 5.2 3 5.2 .3 3 .2 2 2 5.2 .3 7.2 .3 2 .3 5.3 7.2 1
− − = = = − −
c, Ta có :
5 4 9
10 8 8 4 .9 2.6 2 .3 6 .20 − +
= ( ) ( )
10 8 10 8 10 9
10 8 10 8 10 8 2 .3 1 3 2 .3 2 .3 2 1 2 .3 2 .3 .5 2 .3 1 5 6 3 − − − − = = = + +
Bài 5: Thực hiện phép tính:
a,
12 7 15 8
24 14 12 5 15.4 .9 4.3 .8 19.2 .3 6.4 .27 − − b,
15 22 16 4
9 7 5 23 3 .2 6 .4 2.9 .8 7.27 .2 + −
c,
3 10 9
6 12 11 16 .3 120.6 4 .3 6 +
+
HD :
a, Ta có:
12 7 15 8
24 14 12 5 15.4 .9 4.3 .8 19.2 .3 6.4 .27 − −
= ( ) ( )
24 15 2 24 15 26 15
24 14 25 16 24 24 2 2 .3 5 2 5.2 .3 2 .3 3 3 19.2 .3 2 .3 1 2 .3 19 2.3
− − = = = − −
b, Ta có :
15 22 16 4
9 7 5 23 3 .2 6 .4 2.9 .8 7.27 .2 + −
= ( ) ( )
22 15 2 15 22 24 16
22 18 15 23 22 15 3 2 .3 1 2 .3 3 .2 2 .3 13 13 2 .3 7.3 .2 5 5 2 .3 3 7.2
+ + − = = = − − −
c, Ta có: ( ) ( )
( ) ( )
( ) ( )
3 9 4 10 3 12 10 12 10 12 10
6 12 12 11 11 11 11 11 2 12 2 .3 2 .3.5. 2.3 2 .3 1 5 2 .3 2 .3 .5 2.6 12 2 .3 2 .3 2 .3 2.3 1 3.7 21 2 .3 2.3
+ + + = = = = + + +
Bài 6: Thực hiện …
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