Bài 2. > , < ,  = ?

5/7 < 4/3             2/5 < 6/10            1/4 = 3/12                27/36 >

2/9           7/6 > 7/9

7/2 = 2/7        15/23 < 1                  27/9 > 2          14/15 < 1          51/17 < 4

sai rôi

a) 1/2 + 3/4 - (3/4 - 4 - 5)

= 1/2 + 3/4 - 3/4 + 4 + 5

= (3/4 - 3/4) + (4 + 5) + 1/2

= 0 + 9 + 1/2

= 19/2

b) [9/16 + 8/(-27)] - (19/27- 7/16 - 2)

= 9/16 - 8/27 - 19/27 + 7/16 + 2

= (9/16 + 7/16) + (-8/27 - 19/27) + 2

= 1 - 1 + 2

= 2

c) -5/8 . [4/9 + 7/(-12)]

= -5/8 . (-5/36)

= 25/288

d) 7/10 . (-3/5) + 7/10 . (-2/5) - (-3/10)

= 7/10 . (-3/5 - 2/5) + 3/10

= 7/10 . (-1) + 3/10

= -2/5

e) -3/7 . 5/9 + 4/9 . (-3/7) + 2 3/7

= -3/7 . (5/9 + 4/9) + 17/7

= -3/7 . 1 + 17/7

= 2

f) 8 2/7 - (3 4/9 + 4 2/7)

= 8 + 2/7 - 3 - 4/9 - 4 - 2/7

= (8 - 3 - 4) + (2/7 - 2/7) - 4/9

= 1 - 4/9

= 5/9

h) 3.(-1/2)² - (4/5 + 8/15) : 5/6

= 3.1/4 - 4/3 : 5/6

= 3/4 - 8/5

= -17/20

DAI QUA . 

Mai tui giải cho hem

Ta có:

\(A=\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{13.15}\)

\(A=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{15}\)

\(A=\frac{1}{3}-\frac{1}{15}=\frac{4}{15}\)

\(B=2.\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\right)\)

\(B=2.\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)

\(B=2.\left(\frac{1}{1}-\frac{1}{10}\right)=2.\frac{9}{10}\)

\(B=\frac{9}{5}\)

Ok chị. Nhớ là sáng tầm 10h nhé ! Mà chỉ cần giải phần B thui phần A em biết làm rồi .

a: =2/3+2/7=14/21+6/21=20/21

b: =17/18-33/18=-16/18=-8/9

c: =7/12-3/14=49/84-18/84=31/84

d: =-1/4-1/8=-3/8

`@` `\text {Ans}`

`\downarrow`

`a)`

\(\dfrac{3}{4}+\dfrac{2}{3}+\dfrac{3}{5}\)

`=`\(\dfrac{9}{12}+\dfrac{8}{12}+\dfrac{3}{5}\)

`=`\(\dfrac{17}{12}+\dfrac{3}{5}\)

`=`\(\dfrac{85}{60}+\dfrac{36}{60}\)

`=`\(\dfrac{121}{60}\)

`b)`

\(\dfrac{1}{2}\cdot\dfrac{9}{13}\div\dfrac{27}{26}\)

`=`\(\dfrac{1}{2}\cdot\dfrac{9}{13}\cdot\dfrac{26}{27}\)

`=`\(\dfrac{1}{2}\cdot\dfrac{2}{3}\)

`=`\(\dfrac{1}{3}\)

`c)`

\(\dfrac{2}{7}\cdot\dfrac{1}{9}+\dfrac{2}{7}\cdot\dfrac{2}{9}+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{2}{7}\cdot\left(\dfrac{1}{9}+\dfrac{2}{9}\right)+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{2}{7}\cdot\dfrac{1}{3}+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{1}{3}\cdot\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\)

`=`\(\dfrac{1}{3}\cdot1=\dfrac{1}{3}\)

`d)`

\(11\div\dfrac{5}{2}+11\div\dfrac{7}{3}+11\div\dfrac{35}{6}\)

`=`\(11\cdot\dfrac{2}{5}+11\cdot\dfrac{3}{7}+11\cdot\dfrac{6}{35}\)

`=`\(11\cdot\left(\dfrac{2}{5}+\dfrac{3}{7}+\dfrac{6}{35}\right)\)

`=`\(11\cdot1=11\)

a) 3/4 + 2/3 + 3/5 = 45/60 + 40/60 + 36/60 = 121/60

b) 1/2 x 9/13 : 27/26 = 9/26 x 26/27 = 1/3

c) 2/7 x 1/9 + 2/7 x 2/9 + 1/3 x 5/7 = 2/7 x (1/9 + 2/9) + 5/21 = 2/7 x 1/3 + 5/21 = 2/21 + 5/21 = 1/3

d) 11 : 5/2 + 11 : 7:3 + 11 : 35/6 = 11 x (2/5 + 3/7 + 6/35) = 11 x 1 = 11 

1:

a: =23/27-11/17+4/27+28/17

=23/27+4/27+28/17-11/17

=1+1=2

b: \(=\dfrac{2}{3}\cdot\left(\dfrac{7}{9}+\dfrac{2}{9}\right)-\dfrac{2}{9}\)

=2/3-2/9

=6/9-2/9

=4/9

c: \(=\dfrac{11}{5}\cdot\dfrac{7}{3}-\dfrac{1}{3}\cdot\dfrac{11}{5}\)

=11/5(7/3-1/3)

=11/5*2

=22/5

d: \(=\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot...\cdot\dfrac{2024}{2023}=\dfrac{2024}{2}=1012\)

e: \(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{2022}{2023}=\dfrac{1}{2023}\)

`1   5/27 + 7 /23 + 1/2 - 5/27 + 16/23`

` = 32/27 + 7/23 + 1/2 - 5/27 + 16/23 `

`= (32/27 - 5/27 ) + (7/23 + 16/23 ) + 1/2 `

`= 27/27 + 23/23 + 1/2 `

`= 1 + 1 + 1/2 `

`= 5/2`

` 6 1/5 - ( 2/3 . 9/10 - 7/5 )`

` = 31/5 - 2/3 . 9/10 + 7/5 `

`= ( 31/5 + 7/5 ) - ( 2/3 . 9/10 ) `

`= 38/5 - 3/5 `

`= 35/5`

`= 7`

`@ animephamdanhv.`

1: =-2/9(15/17+2/17)=-2/9

2: \(=\dfrac{-6}{3}+\dfrac{-21}{90}\)

=-2-7/30=-67/30

3: \(=\dfrac{3}{4}\cdot\dfrac{7}{5}+\dfrac{9}{7}\cdot\dfrac{3}{2}\)

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

1: =-2/9(15/17+2/17)=-2/9

2: =34⋅75+97⋅32=34⋅75+97⋅32

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

-2/15

-4/35

-5/3

10

-8/3

-7/2

-9

-4/3

Chúc em học giỏi

\(=\dfrac{-2}{15}\\ =\dfrac{-4}{35}\\ =-1\\ =10\\ =\dfrac{-8}{3}\\ =-7\\ =-9\\ =\dfrac{-4}{3}\)

-2/15

-4/35

-5/3

10

-8/3

-7/2

-9

-4/3