Bài 1: 

a: =-3/7

b: =-3/5

c: =1/13

d: =-1/2

Bài 2: 

a: \(=\dfrac{21\cdot11}{22\cdot9}=\dfrac{1}{2}\cdot\dfrac{7}{3}=\dfrac{7}{6}\)

b: \(=\dfrac{49\cdot8}{10}=\dfrac{196}{5}\)

a \(\dfrac{-2}{5}\)

b -1

c \(\dfrac{2}{5}\)

d \(\dfrac{-18}{11}\)

a) \(\dfrac{7}{56}=\dfrac{7:7}{56:7}=\dfrac{1}{8}\)

b) \(\dfrac{25}{100}=\dfrac{25:25}{100:25}=\dfrac{1}{4}\)

a) 7/56=7:7/56:7=1/8

b) 25/100=25:25/100:25=1/4

25100=25:25100:25=14

9/10

19/21

9/10

19/21

a.9/10

b.19/21

bạn tham khảo :
Câu hỏi của hoang van binh - Toán lớp 4 - Học trực tuyến OLM

tham khảo :}
Câu hỏi của hoang van binh - Toán lớp 4 - Học trực tuyến OLM

Tham khảo

a: \(A=\dfrac{2\cdot8^4\cdot27^2+44\cdot6^9}{2^7\cdot6^7+2^7\cdot40\cdot9^4}\)

\(=\dfrac{2\cdot2^{12}\cdot3^6+2^2\cdot11\cdot2^9\cdot3^9}{2^7\cdot3^7\cdot2^7+2^7\cdot2^3\cdot5\cdot3^8}\)

\(=\dfrac{2^{13}\cdot3^6+2^{11}\cdot3^9\cdot11}{2^{14}\cdot3^7+2^{10}\cdot5\cdot3^8}\)

\(=\dfrac{2^{11}\cdot3^6\left(2^2+3^3\cdot11\right)}{2^{10}\cdot3^7\left(2^4+5\cdot3\right)}\)

\(=\dfrac{2\cdot301}{3\cdot31}=\dfrac{602}{93}\)

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Bài 2: So sánh các phân số sau

7/15 > 5/13              11/12 > 7/48        24/35 > 21/7           15/26 > 7/8

a: \(\dfrac{4\cdot5+4\cdot11}{8\cdot7+4\cdot3}=\dfrac{4\cdot16}{4\left(2\cdot7+3\right)}=\dfrac{16}{17}=\dfrac{11088}{11781}\)

\(\dfrac{-15\cdot8+10\cdot7}{5\cdot6+20\cdot3}=\dfrac{-120+170}{30+60}=\dfrac{50}{90}=\dfrac{5}{9}=\dfrac{6545}{11781}\)

\(\dfrac{2^4\cdot5^2\cdot7}{2^3\cdot5\cdot7^2\cdot11}=2\cdot5\cdot\dfrac{1}{77}=\dfrac{10}{77}=\dfrac{1530}{11781}\)

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

\(\dfrac{121212}{363636}=\dfrac{121212\div121212}{363636\div121212}=\dfrac{1}{3}\)

\(\dfrac{121212}{363636}=\dfrac{121212\div10101}{363636\div10101}=\dfrac{12}{36}=\dfrac{1}{3}\)

a)\(\dfrac{5}{25}=\dfrac{1}{5}\)
\(\dfrac{75}{100}=\dfrac{3}{4}\)
\(\dfrac{64}{720}=\dfrac{4}{45}\)
\(\dfrac{16}{1000}=\dfrac{2}{125}\)
b)\(\dfrac{4}{6}=\dfrac{2}{3}\)
\(\dfrac{12}{8}=\dfrac{3}{2}\)
\(\dfrac{15}{25}=\dfrac{3}{5}\)
\(\dfrac{11}{22}=\dfrac{1}{2}\)
c)\(\dfrac{5}{10}=\dfrac{1}{2}\)
\(\dfrac{12}{36}=\dfrac{1}{3}\)

\(\dfrac{9}{72}=\dfrac{1}{8}\)

\(\dfrac{75}{300}=\dfrac{1}{4}\)
d)\(\dfrac{14}{28}=\dfrac{1}{2}\)
\(\dfrac{25}{50}=\dfrac{1}{2}\)
\(\dfrac{48}{30}=\dfrac{8}{5}\)
\(\dfrac{81}{54}=\dfrac{3}{2}\)

a: 5/25=1/5

75/100=3/4

64/720=4/45

16/1000=2/125

b: 4/6=2/3

12/8=3/2

15/25=3/5

11/22=1/2

c: 5/10=1/2

12/36=1/3

9/72=1/8

75/300=1/4

d: 14/28=1/2

25/50=1/2

48/30=8/5

81/54=3/2