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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Đáp án cần chọn là: B

9.8 − 7.18 3 2 .10 = 9.8 − 7.9.2 9.10 = 8 − 14 10 = − 3 5 16   .19 − 26   .   19 57   .   3 − 19 = 16   .19 − 26   .   19 19.3   .   3 − 19 = 16 − 26 9 − 1 = − 5 4

MSC = 20

− 3 5 = − 3.4 5.4 = − 12 20 ;     − 5 4 = − 5.5 4.5 = − 25 20

Vậy sau khi quy đồng ta được hai phân số:    − 12 20 và  − 25 20 .

a: 12/21=4/7=8/14

4/56=1/14

b: 12/15=4/5=24/30

6/36=1/6=5/30

15/50=3/10=9/30

c: 63/77=9/11=81/99

60/108=5/9=55/99

-18/27=-2/3=-66/99

d: -26/-156=1/6=7/42

49/-14=-7/2=-147/42

32/112=2/7=12/42

+)

\(\frac{1}{2}=\frac{6}{12};\frac{1}{3}=\frac{4}{12};-\frac{1}{12}\)

+)

\(\frac{9}{30}=\frac{3}{10}=\frac{12}{40};\frac{98}{80}=\frac{49}{40}\)

1/2=6/12   1/3=4/12  -1/12=-1/12

9/30=3/10    98/80=49/40

3/10=12/40  49/40=49/40

Ta có : 

\(\frac{1}{2}=\frac{1.6}{2.6}=\frac{6}{12}\)

\(\frac{1}{3}=\frac{1.4}{3.4}=\frac{4}{12}\)

\(-\frac{1}{12}\)

Vậy quy đồng mẫu số các phân số : \(\frac{1}{2};\frac{1}{3};-\frac{1}{12}\)ta được : \(\frac{6}{12};\frac{4}{12};-\frac{1}{12}\)

Ta có : 

\(\frac{9}{30}=\frac{9:3}{30:3}=\frac{3}{10};\frac{98}{80}=\frac{98:2}{80:2}=\frac{49}{40}\)

Lại có : \(\frac{3}{10}=\frac{3.4}{10.4}=\frac{12}{40}\)

Vậy quy đồng mẫu số các phân số \(\frac{9}{30};\frac{98}{80}\)ta được : \(\frac{12}{40};\frac{49}{40}\)

~ Ủng hộ nhé 

၁၁မန််ခခခ

`Answer:`

`a)` Ta có:

\(\frac{29-5}{54}=\frac{4}{9}\)

\(\frac{45-54}{33}=-\frac{3}{11}\)

Mẫu chung là `99`

\(\Rightarrow\frac{4}{9}=\frac{4.11}{9.11}=\frac{44}{99}\)

\(\Rightarrow\frac{-3}{11}=\frac{\left(-3\right).9}{11.9}=-\frac{27}{99}\)

`b)` Ta có:

\(\frac{18+14}{18}=\frac{16}{4}\)

\(\frac{26-50}{30}=-\frac{4}{5}\)

Mẫu chung là `45`

\(\Rightarrow\frac{16}{9}=\frac{16.5}{9.5}=\frac{80}{45}\)

\(\Rightarrow-\frac{4}{5}=\frac{\left(-4\right).9}{5.9}=-\frac{36}{45}\)

\(a,\frac{297}{891}=\frac{1}{3}\)

\(b,\frac{474}{1185}=\frac{2}{5}\)

\(c,\frac{549}{1281}=\frac{3}{7}\)

\(d,\frac{3672}{4284}=\frac{6}{7}\)

\(e,\frac{7976}{9970}=\frac{4}{5}\)

a, \(\frac{297}{891}\)= \(\frac{1}{3}\)

b,\(\frac{474}{1185}\)=\(\frac{2}{5}\)

c, \(\frac{549}{1281}\)=\(\frac{3}{7}\)

d,\(\frac{7976}{9970}\)=\(\frac{4}{5}\)

Học tốt nha !

cảm ơn hai cậu

\(a.\dfrac{5}{10}=\dfrac{1}{2}=\dfrac{1\times3}{2\times3}=\dfrac{3}{6}\)

\(\dfrac{25}{75}=\dfrac{1}{3}=\dfrac{1\times2}{3\times2}=\dfrac{2}{6}\)

\(b.\dfrac{42}{56}=\dfrac{3}{4}=\dfrac{3\times2}{4\times2}=\dfrac{6}{8}\)

\(\dfrac{18}{48}=\dfrac{3}{8}\)

\(c.\dfrac{27}{81}=\dfrac{1}{3}=\dfrac{1\times4}{3\times4}=\dfrac{4}{12}\)

\(\dfrac{57}{76}=\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)

\(\dfrac{35}{84}=\dfrac{5}{12}\)

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a.3/6 va 2/6     b.24/32 va12/32  c.912/2736  2052/2736 1140/2736