a)36/48>12/48

=>6/8>3/12

b)135/225<180/225

=>15/25<36/45

c)1575/2835>1323/2835

=>15/27>49/105

Chúc e học tốt

a) mẫu số chung: 4

\(\dfrac{6}{8}=\dfrac{6:2}{8:2}=\dfrac{3}{4};\dfrac{3}{12}=\dfrac{3:3}{12:3}=\dfrac{1}{4}\)

vì \(\dfrac{3}{4}>\dfrac{1}{4}\)nên \(\dfrac{6}{8}>\dfrac{3}{12}\)

b) mẫu số chung: 5

\(\dfrac{15}{25}=\dfrac{15:5}{25:5}=\dfrac{3}{5};\dfrac{36}{45}=\dfrac{36:9}{45:9}=\dfrac{4}{5}\)

vì\(\dfrac{3}{5}< \dfrac{4}{5}\)nên \(\dfrac{15}{25}< \dfrac{36}{45}\)

5/7<3/4

8/9>5/6

a) \(\dfrac{5}{7}< \dfrac{3}{4}\)

b) \(\dfrac{8}{9}>\dfrac{5}{6}\)

15/17       >      25/27

15/17   >   25/27

Câu 3:

a) \(\dfrac{12}{36}=\dfrac{12:12}{36:12}=\dfrac{1}{3}\)

\(\dfrac{-16}{20}=\dfrac{-16:4}{20:4}=\dfrac{-4}{5}\)

b) \(\dfrac{21}{105}=\dfrac{21:21}{105:21}=\dfrac{1}{5}\)

\(\dfrac{35}{150}=\dfrac{35:5}{150:5}=\dfrac{7}{30}\)

Câu 4: 

a) \(\dfrac{3}{10}+\dfrac{5}{10}=\dfrac{3+5}{10}=\dfrac{8}{10}=\dfrac{4}{5}\)

b) Ta có: \(\left(-27\right)\cdot36+64\cdot\left(-27\right)+23\cdot\left(-100\right)\)

\(=\left(-27\right)\cdot\left(64+36\right)+23\cdot\left(-100\right)\)

\(=-27\cdot100-23\cdot100\)

\(=100\left(-27-23\right)\)

\(=-50\cdot100=-5000\)

c) \(\dfrac{5}{8}+\dfrac{3}{12}=\dfrac{15}{24}+\dfrac{6}{24}=\dfrac{21}{24}=\dfrac{7}{8}\)

d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)

\(=\left(-\dfrac{2}{17}+\dfrac{-15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)

\(=-1+1+\dfrac{5}{6}\)

\(=\dfrac{5}{6}\)

Ta có:

15/17<25/27 nên 15/17<25/27

ta có

15/17>25/27

nen 15/17<25/27

Co j góc lệch cùng trời cuối đất cú mèo

Ta có : \(\frac{3}{-4}=\frac{-3}{4}< 0\)

\(\frac{-1}{-4}=\frac{1}{4}>0\)

\(\Rightarrow\frac{3}{-4}< \frac{-1}{-4}\) hay \(\frac{-3}{4}< \frac{1}{4}\)

Vậy : ....

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