Câu 1:

A = (a x 7 + a x 8 - a x 15) : (1 + 2 + 3 + ........ + 10)

A = a x(7+8-15) : (1+2+3+...+10)

A = a x 0 : (1+2+3+...+10)

A = 0: (1+2+3+4+...+10)

A = 0

Câu 2:

B = (18 - 9 x 2) x (2 + 4 + 6 + 8 + 10)

B = (18 - 18)  x (2+4+6+8+10)

B  = 0 x ( 2 + 4 + 6 + 8 +10)

B   = 0

Giáng sinh vui vẻ nhé !

A = {a x (7 + 8 - 15 ) }:  (1+2+3+4+........+10)

=  {a x 0 } :  (1+2+3+4+........+10)

= 0 : (1+2+3+4+........+10)

= 0

đây câu A đây

A) 137/ 12

B) 4

C) 5

b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16

= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8

= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)

= 1 + 1 + 7/4

= 2 + 7/4 = 15/4

c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16 

= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2

= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2

= 14/7 + 12/6 + 5/8 + 1/2

= 2 + 2 + 5/8 + 1/2

= 4 + 9/8 = 41/8

Tính nhanh mỗi biểu thức sau:

a, 0 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20

= (0 + 20) + (1 + 19) + (2 + 18) + (3 + 17) + (4 + 16) + (5 + 15) + (6 + 14) + (7 + 13) + (8 + 12) + (9 + 11) + 10

= 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 20 + 10

= 20 x 10 + 10

= 200 + 10

= 210

b, 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (4 x 9 - 36)

= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x (36 - 36)

= 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 0

= A x 0

= 0

c, (81 - 7 x 9 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= (81 - 63 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= (18 - 18) : (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= 0 :(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= 0 : A

= 0

d, (6 x 5 + 7 - 37) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= (30 + 7 - 37)  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= (37 - 37)  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= 0  x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)

= 0 x A

= 0

e, (11 x 9 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)

= (99 - 100 + 1) : (1 x 2 x 3 x 4 x ... x 10)

= (99 + 1 - 100) : (1 x 2 x 3 x 4 x ... x 10)

= (100 - 100) : (1 x 2 x 3 x 4 x ... x 10)

= 0 : (1 x 2 x 3 x 4 x ... x 10)

= 0 : A

= 0

g, (m : 1 - m x 1) : (m x 2008 + m x 2008)

= (m - m) : (m x 2008 + m x 2008)

= 0 : (m x 2008 + m x 2008)

= 0 : A

= 0

h, (2 + 4 + 6 + 8 + m x n) x (324 x 3 - 972)

= (2 + 4 + 6 + 8 + m x n) x (972 - 972)

= (2 + 4 + 6 + 8 + m x n) x 0

= A x 0

= 0

l, (1 + 2 + 3 + ... + 99)  x (13 x 15 - 12 x 15 - 15)

= (1 + 2 + 3 + ... + 99) x (15 x (13 - 12 - 1))

= (1 + 2 + 3 + ... + 99) x (15 x 0)

= (1 + 2 + 3 + ... + 99) x 0

= A x 0

= 0

i, (0 x 1 x 2 x...x 99 x 100) : (2 + 4 + 6 +...+ 98)

= 0 x : (2 + 4 + 6 +...+ 98)

= 0 x A

= 0

k, (0 + 1 + 2 +...+ 97 + 99) x (45 x 3 - 45 x 2 - 45)

= (0 + 1 + 2 +...+ 97 + 99) x (45 x (3 - 2 - 4))

= (0 + 1 + 2 +...+ 97 + 99) x (45 x 0)

= (0 + 1 + 2 +...+ 97 + 99) x 0

= A x 0

= 0

GIÚP MÌNH VỚI  

(-7) NHÂN (-24) + (-36) : (-3)^2 - (-5)^3

a: =7/12+6/36

=7/12+2/12=9/12=3/4

b: =8/9-2/3=8/9-6/9=2/9

c: \(=\dfrac{7\cdot2+5\cdot3}{18}\cdot\dfrac{3}{5}=\dfrac{29}{18}\cdot\dfrac{3}{5}=\dfrac{87}{90}=\dfrac{29}{30}\)

a) \(\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\dfrac{6}{36}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

b) \(\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\dfrac{4}{15}\times\dfrac{5}{2}=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{2}{9}\)

c) \(\left(\dfrac{7}{9}+\dfrac{5}{6}\right)\times\dfrac{3}{5}=\dfrac{29}{18}\times\dfrac{3}{5}=\dfrac{87}{90}=\dfrac{29}{30}\)

Bài 2:

a: 2/6x5/3=10/18=5/9

b: 11/9x5/10=55/90=11/18

c: 3/9x6/8=1/3x3/4=1/4

d: 4/9x12/16=48/144=1/3

e: 25/15x6/7=5/3x6/7=30/21=10/7

f: 6/10x15/20=90/200=9/20

Bài 1

4/5 x 6/7= 24/35

2/9 x 1/2= 2/18= 1/9

1/2 x 8/3= 8/6= 4/3

7/9 x 6/5= 42/45= 14/15

8/7 x 5/9= 40/63

10/11 x 22/15= 220/165= 4/3

Bài 2

2/6 x 5/3= 1/3 x 5/3=5/9

11/9 x 5/10= 11/9 x 1/2= 11/18

3/9 x 6/8= 1/3 x 3/4 =3/12= 1/4

4/9 x 12/16= 4/9 x 3/4= 12/36= 1/3

25/15 x 6/7= 5/3 x 6/7= 30/21= 10/7

6/10 x 15/20= 3/5 x 3/4= 9/20

Giải chi tiết cho mình nha

2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5

`4/7+4`

`=4/7+4/1`

`=4/7+28/7`

`=32/7`

__

`3+6/11`

`=33/11+6/11`

`=39/11`

__

`3-5/7`

`=3/1-5/7`

`=21/7-5/7`

`=16/7`

__

`21/9-2`

`=21/9-18/9`

`=3/9`

`=1/3`

__

`15/24+2`

`=15/24+48/24`

`=63/24`

`=21/16`

__

`63/45-20/25`

`=63/45-4/5`

`=63/45-36/45`

`=27/45`

`=9/15`

__

`3/4-2/8`

`=3/4-1/4`

`=2/4`

__

`6/7-5/8`

`=48/56-35/56`

`=13/56`

__

`37/45-5/9`

`=37/45-25/45`

`=12/45`

`=4/15`

__

`46/39-11/13`

`=46/39-33/39`

`=13/39`

`=1/2`

__

`5/12+3/4+1/3`

`=5/12+9/12+4/12`

`=14/12+4/12`

`=18/12`

`=3/2`

__

`1/2+3/7+11/14`

`=7/14+6/14+11/14`

`=13/14+11/14`

`=24/14`

`=12/7`

__

`7/10-(1/5+1/4)`

`=7/10-(4/20+5/20)`

`=7/10-9/20`

`=14/20-9/20`

`=5/20`

`=1/4`

__

`15/4-2/3-3/4`

`=(15/4-3/4)-2/3`

`=12/4-2/3`

`=3-2/3`

`=9/3-2/3`

`=7/3`

Bài 1 : tính 

`A ) 7 / 8  + 5 / 12 = 21/24 + 10/24 = 31/24`                                         

`B ) 19 / 15 - 5 / 6 = 38/30 - 25/30 = 13/30 `

`C ) 8 / 21 xx 14 / 5 =16/15      `                                        

`D ) 9 / 7 : 3 / 4 = 9/7 xx 4/3 = 12/7`