168/210;245/210;270/210

7/1 và 9/2

Mẫu chung 2

 81/7 và 9/21

Mẫu chung 21

\(\dfrac{7\times2}{1\times2}=\dfrac{14}{2}.và.\dfrac{9}{2};\dfrac{81\times3}{7\times3}=\dfrac{243}{21}và\dfrac{9}{21}\)

Ta có: 

`11/10 = 1 + 1/10`

`7/6 = 1+1/6`

`10/9 = 1 + 1/9`

`9/8 = 1 + 1/8`

Ta có: `1/10 < 1/9 < 1/8 < 1/6`

nên `11/10 < 10/9  < 9/8 < 7/6`

\(\dfrac{3}{2}=\dfrac{3\times225}{2\times225}=\dfrac{675}{450}\)

\(\dfrac{7}{9}=\dfrac{7\times50}{9\times50}=\dfrac{350}{450}\)

\(\dfrac{4}{25}=\dfrac{4\times18}{25\times18}=\dfrac{72}{450}\).

\(\dfrac{3}{2}\text{=}\dfrac{3\times225}{2\times225}\text{=}\dfrac{675}{450}\)

\(\dfrac{7}{9}\text{=}\dfrac{7\times50}{9\times50}\text{=}\dfrac{350}{450}\)

\(\dfrac{4}{25}\text{=}\dfrac{4\times18}{25\times18}\text{=}\dfrac{72}{450}\)

500/60

36/60

35/60

150/60

156/60

500/60, 36/60, 35/60, 150/60, 156/60

\(\dfrac{4}{25}=\dfrac{4\times4}{25\times4}=\dfrac{16}{100}\\ \dfrac{-7}{4}=\dfrac{-7\times25}{4\times25}=\dfrac{-175}{100}\\ \dfrac{9}{50}=\dfrac{9\times2}{50\times2}=\dfrac{18}{100}\)

MSC : 360

`5/8 = (5xx45)/(8xx45)=225/360`

`7/20=(7xx18)/(20xx18)=126/360`

`-4/9=(-4xx40)/(9xx40)=-160/360`

=50/180;63/180;-80/180

1a. chọn mẫu chung là 120,ta có

\(\frac{7}{30}=\frac{7.4}{30.4}=\frac{28}{120}\)

\(\frac{13}{60}=\frac{13.2}{60.2}=\frac{26}{120}\)

\(\frac{-9}{40}=\frac{-9.3}{40.3}=\frac{27}{120}\)

vậy....

1b. chon mẫu số chung là 60

\(\frac{3}{-20}=\frac{-3.3}{20.3}=-\frac{9}{60}\)

\(\frac{-11}{-30}=\frac{-11.\left(-2\right)}{-30.\left(-2\right)}=\frac{22}{60}\)

\(\frac{7}{15}=\frac{7.4}{15.4}=\frac{28}{60}\)

2a.\(\frac{-15}{90}=\frac{-1}{6};\frac{120}{600}=\frac{1}{5};\frac{-75}{150}=\frac{-1}{2}\)

mẫu chung 30

\(\frac{-1}{6}=-\frac{5}{30};\frac{1}{5}=\frac{16}{30};-\frac{1}{2}=\frac{-15}{30}\)

vậy...

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MSC:60 NHA BẠN 

ko bé ơi 

lớp tui có bạn cũng tên Nguyễn Trung Hiếu

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