`40/35= 8/7`

`8=8->40/35=8/7`

18/24=3/4

15/25=3/5

21/15=7/5

28/24=9/8

Hok tốt

Cách 1 :

Rút gọn : 12/16 = 3/4  ,   28/21 = 4/3

So sánh : 12/16 < 28/21

Cách 2 :

So sánh Vì 12/16 < 1 và 28/ 21 > 1 nên 28/21 > 12/16

1: B là số nguyên

=>n-3 thuộc {1;-1;5;-5}

=>n thuộc {4;2;8;-2}

3:

a: -72/90=-4/5
b: 25*11/22*35

\(=\dfrac{25}{35}\cdot\dfrac{11}{22}=\dfrac{5}{7}\cdot\dfrac{1}{2}=\dfrac{5}{14}\)

c: \(\dfrac{6\cdot9-2\cdot17}{63\cdot3-119}=\dfrac{54-34}{189-119}=\dfrac{20}{70}=\dfrac{2}{7}\)

\(\frac{16}{48}=\frac{16:16}{48:16}=\frac{1}{3}\);\(\frac{14}{35}=\frac{14:7}{35:7}=\frac{2}{5}\)

\(\frac{1}{3}=\frac{1\cdot5}{3\cdot5}=\frac{5}{15}\);    \(\frac{2}{5}=\frac{2\cdot3}{5\cdot3}=\frac{6}{15}\)

\(\frac{5}{7}\)và\(\frac{6}{21}\)

\(\frac{6}{21}=\frac{2}{7}\)

\(\frac{5}{7}>\frac{2}{7}\)

\(\frac{5}{7}\) và \(\frac{6}{21}\)

\(\frac{6}{21}=\frac{2}{7}\)

\(\Rightarrow\frac{5}{7}>\frac{2}{7}\)

ko sai đâu

404/303=4/3

4/3=4/3

2121/3535=21/35

31/35>21/35

Ta có :\(\frac{404}{303}\)= \(\frac{4}{3}\)nên \(\frac{404}{303}=\frac{4}{3}\)

Ta có : \(\frac{31}{35}\)giữ nguyên và \(\frac{2121}{3535}\)= \(\frac{21}{35}\)

Vậy \(\frac{31}{35}>\frac{21}{35}\)

Chúc bạn học giỏi !

a) 

\(\dfrac{6}{12}=\dfrac{6:6}{12:6}=\dfrac{1}{2}\)

\(\Rightarrow\dfrac{1}{2}=\dfrac{1\times2}{2\times2}=\dfrac{2}{4}\)

Mà \(\dfrac{2}{4}< \dfrac{3}{4}\)

Vậy \(\dfrac{6}{12}< \dfrac{3}{4}\).

b)

\(\dfrac{8}{10}=\dfrac{8:2}{10:2}=\dfrac{4}{5}\)

Mà \(\dfrac{2}{5}< \dfrac{4}{5}\)

Vậy \(\dfrac{2}{5}< \dfrac{8}{10}\).

c)

\(\dfrac{40}{35}=\dfrac{40:5}{35:5}=\dfrac{8}{7}\)

Mà \(\dfrac{8}{7}>\dfrac{6}{7}\)

Vậy \(\dfrac{40}{35}>\dfrac{6}{7}\).

d)

\(\dfrac{8}{16}=\dfrac{8:8}{16:8}=\dfrac{1}{2}\)

Mà \(\dfrac{1}{2}< \dfrac{5}{2}\)

Vậy \(\dfrac{8}{16}< \dfrac{5}{2}\).