A, \(\dfrac{7}{9}\) = \(\dfrac{7\cdot5}{9\cdot5}\) = \(\dfrac{35}{45}\)               \(\dfrac{3}{5}\) = \(\dfrac{3\cdot9}{5\cdot9}\) = \(\dfrac{27}{45}\) 

      Vậy \(\dfrac{7}{9}\) > \(\dfrac{3}{5}\) 

B, \(\dfrac{3}{4}\) = \(\dfrac{3\cdot6}{4\cdot6}\) = \(\dfrac{18}{24}\)               \(\dfrac{5}{6}\) = \(\dfrac{5\cdot4}{6\cdot4}\) = \(\dfrac{20}{24}\)

      Vậy \(\dfrac{3}{4}\) < \(\dfrac{5}{6}\)

C, \(\dfrac{1}{4}\) = \(\dfrac{1\cdot3}{4\cdot3}\) = \(\dfrac{3}{12}\)               \(\dfrac{2}{3}\) = \(\dfrac{2\cdot4}{3\cdot4}\) = \(\dfrac{8}{12}\) 

      Vậy \(\dfrac{1}{4}\) < \(\dfrac{2}{3}\) 

D, \(\dfrac{8}{9}\) = \(\dfrac{8\cdot2}{9\cdot2}\) = \(\dfrac{16}{18}\)                \(\dfrac{1}{2}\) = \(\dfrac{1\cdot9}{2\cdot9}\) = \(\dfrac{9}{18}\) 

      Vậy \(\dfrac{8}{9}\) > \(\dfrac{1}{2}\) 

 \(\cdot\) là dấu nhân

-5/4 =-30/24

 7/6 = 28/24

 3/8 = 9/24

 15/24 giữ nguyên

\(\frac{3}{5}=\frac{3\times8}{5\times8}=\frac{24}{40}\)

\(\frac{3}{8}=\frac{3\times5}{8\times5}=\frac{15}{40}\)

\(\frac{3}{10}=\frac{3\times4}{10\times4}=\frac{12}{40}\)

\(\frac{3}{2}=\frac{3\times20}{2\times20}=\frac{60}{40}\)

ghi thiếu bạn ơi

10000000000000000000000000000

\(\frac{3}{5}=\frac{24}{40};\frac{3}{8}=\frac{15}{40};\frac{3}{10}=\frac{12}{40};\frac{3}{2}=\frac{60}{40}\)

\(\frac{3}{5}=\frac{3\times8}{5\times8}=\frac{24}{40}\)

\(\frac{3}{8}=\frac{3\times5}{8\times5}=\frac{15}{40}\)

\(\frac{3}{10}=\frac{3\times4}{10\times4}=\frac{12}{40}\)

\(\frac{3}{2}=\frac{3\times20}{2\times20}=\frac{60}{40}\)

\(\frac{3}{5}=\frac{3\times8}{5\times8}=\frac{24}{40}\)

\(\frac{3}{8}=\frac{3\times5}{8\times5}=\frac{15}{40}\)

\(\frac{3}{10}=\frac{3\times4}{10\times4}=\frac{12}{40}\)

\(\frac{3}{2}=\frac{3\times20}{2\times20}=\frac{60}{40}\)

Bài 3 : 

a: \(MSC:12\\ \dfrac{4}{3}=\dfrac{4\times4}{3\times4}=\dfrac{16}{12};\dfrac{3}{4}=\dfrac{3\times3}{3\times4}=\dfrac{9}{12}\)

b: \(MSC:12\\ \dfrac{5}{4}=\dfrac{5\times3}{4\times3}=\dfrac{15}{12};\dfrac{5}{6}=\dfrac{5\times2}{6\times2}=\dfrac{10}{12}\)

c:\(MSC:24\\ \dfrac{3}{8}=\dfrac{3\times3}{8\times3}=\dfrac{9}{24};\dfrac{1}{6}=\dfrac{1\times2}{6\times2}=\dfrac{2}{12}\)

d: \(MSC:35\\ \dfrac{2}{5}=\dfrac{2\times7}{5\times7}=\dfrac{14}{35};\dfrac{4}{7}=\dfrac{4\times5}{7\times5}=\dfrac{20}{35}\)

Bài 3: 

a: 4/3=16/12

3/4=9/12

b: 5/4=30/24

5/6=20/24

c: 3/8=18/48

1/6=8/48

d: 2/5=14/35

4/7=20/35

Bài 4: 

a: 7/12=28/48

5/48=5/48

b: 4/100=4/100

8/25=32/100

20/35

bài3

1. \(\frac{4}{3}\)= \(\frac{4x4}{3x4}\)=\(\frac{20}{12}\)

\(\frac{3}{4}\)=\(\frac{3x3}{4x3}\)=\(\frac{9}{12}\)

2.\(\frac{5}{4}\)=\(\frac{5x6}{4x6}\)=\(\frac{30}{24}\)

\(\frac{5}{6}\)=\(\frac{5x4}{6x4}\)=\(\frac{20}{24}\)

3.\(\frac{3}{8}\)=\(\frac{3x6}{8x6}\)=\(\frac{18}{48}\)

\(\frac{1}{6}\)=\(\frac{1x6}{6x8}\)=\(\frac{6}{48}\)

4.\(\frac{2}{5}\)=\(\frac{2x7}{5x7}\)=\(\frac{14}{35}\)

\(\frac{4}{7}\)=\(\frac{4x5}{7x5}\)=\(\frac{20}{35}\)

TL

Phân số là 3/45/4

HT

Sao lại thế

Câu 1:

MSC=60

7/10=7.6/10.6=42/60            5/-12=-5/12=-5.5/12.5=-25/60

Câu 2:

17/34=1/2;  -12/22=-6/11;  -25/35=-5/7;  125/75=5/3

Câu 3:

MSC=24

1/3=1.8/3.8=8/24     -3/8=-3.3/8.3=-9/24           17/24=17/24

\(\dfrac{1}{8}=\dfrac{1\times3}{8\times3}=\dfrac{3}{24}\\ \dfrac{2}{3}=\dfrac{2\times8}{3\times8}=\dfrac{16}{24}\\ \dfrac{5}{2}=\dfrac{5\times12}{2\times12}=\dfrac{60}{24}\)

Bài 1: 

a: 3/4=54/72

-1/9=-8/72

-5/8=-45/72

b: -1/7=-8/56

-1/-8=1/8=7/56

3/4=42/56