a; Cách một: 

     \(\dfrac{2}{9}\) = \(\dfrac{2\times2}{9\times2}\) = \(\dfrac{4}{18}\)  < \(\dfrac{4}{10}\) Vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

     \(\dfrac{4}{9}\) = \(\dfrac{4\times3}{9\times3}\) = \(\dfrac{12}{27}\); \(\dfrac{6}{10}\) = \(\dfrac{6\times2}{10\times2}\) = \(\dfrac{12}{20}\) 

 Vì \(\dfrac{12}{27}\) < \(\dfrac{12}{20}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{12}{20}\)

     \(\dfrac{3}{8}\) = \(\dfrac{3\times4}{8\times4}\) = \(\dfrac{12}{24}\);   \(\dfrac{4}{7}\) = \(\dfrac{4\times3}{7\times3}\) = \(\dfrac{12}{21}\)

Vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

    \(\dfrac{5}{9}\) = \(\dfrac{5\times7}{9\times7}\) = \(\dfrac{35}{63}\); \(\dfrac{7}{10}\) = \(\dfrac{7\times5}{10\times5}\) = \(\dfrac{35}{50}\)

Vì \(\dfrac{35}{63}\) < \(\dfrac{35}{50}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\)

       Cách hai:

a; \(\dfrac{2}{9}\) = \(\dfrac{2\times10}{9\times10}\) = \(\dfrac{20}{90}\); \(\dfrac{4}{10}\)  = \(\dfrac{4\times9}{10\times9}\) = \(\dfrac{36}{90}\) 

Vì \(\dfrac{20}{90}\) < \(\dfrac{36}{90}\) vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

b; \(\dfrac{4}{9}\) = \(\dfrac{4\times10}{9\times10}\) = \(\dfrac{40}{90}\); \(\dfrac{6}{10}\) = \(\dfrac{6\times9}{10\times9}\) = \(\dfrac{54}{90}\)

   Vì \(\dfrac{40}{90}\) < \(\dfrac{54}{90}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{6}{10}\)

c; \(\dfrac{3}{8}\) = \(\dfrac{3\times7}{8\times7}\) = \(\dfrac{21}{56}\); \(\dfrac{4}{7}\) =  \(\dfrac{4\times8}{7\times8}\) = \(\dfrac{32}{56}\)

Vì \(\dfrac{21}{56}\) < \(\dfrac{32}{56}\) vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

d; \(\dfrac{5}{9}\) = \(\dfrac{5\times10}{9\times10}\) = \(\dfrac{50}{90}\); \(\dfrac{7}{10}\) = \(\dfrac{7\times9}{10\times9}\) = \(\dfrac{63}{90}\)

Vì \(\dfrac{50}{90}\) < \(\dfrac{63}{90}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\) 

     Cách ba:

a; \(\dfrac{2}{9}\) < \(\dfrac{2+2}{9+2}\) = \(\dfrac{4}{11}\) < \(\dfrac{4}{10}\) vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

b; \(\dfrac{4}{9}\) < \(\dfrac{4+2}{9+2}\) < \(\dfrac{6}{11}\) < \(\dfrac{6}{10}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{6}{10}\)

c; \(\dfrac{3}{8}\) < \(\dfrac{3+1}{8+1}\) = \(\dfrac{4}{9}\) < \(\dfrac{4}{7}\) vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

d; \(\dfrac{5}{9}\) < \(\dfrac{5+2}{9+2}\) = \(\dfrac{7}{11}\) < \(\dfrac{7}{10}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\)

giúp mình nhanh nha ❤

a , 2/9 > 4/10

Nhầm a điền dấu < nha

a; Cách một: 

     \(\dfrac{2}{9}\) = \(\dfrac{2\times2}{9\times2}\) = \(\dfrac{4}{18}\)  < \(\dfrac{4}{10}\) Vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

     \(\dfrac{4}{9}\) = \(\dfrac{4\times3}{9\times3}\) = \(\dfrac{12}{27}\); \(\dfrac{6}{10}\) = \(\dfrac{6\times2}{10\times2}\) = \(\dfrac{12}{20}\) 

 Vì \(\dfrac{12}{27}\) < \(\dfrac{12}{20}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{12}{20}\)

     \(\dfrac{3}{8}\) = \(\dfrac{3\times4}{8\times4}\) = \(\dfrac{12}{24}\);   \(\dfrac{4}{7}\) = \(\dfrac{4\times3}{7\times3}\) = \(\dfrac{12}{21}\)

Vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

    \(\dfrac{5}{9}\) = \(\dfrac{5\times7}{9\times7}\) = \(\dfrac{35}{63}\); \(\dfrac{7}{10}\) = \(\dfrac{7\times5}{10\times5}\) = \(\dfrac{35}{50}\)

Vì \(\dfrac{35}{63}\) < \(\dfrac{35}{50}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\)

     Cách hai:

a; \(\dfrac{2}{9}\) = \(\dfrac{2\times10}{9\times10}\) = \(\dfrac{20}{90}\); \(\dfrac{4}{10}\)  = \(\dfrac{4\times9}{10\times9}\) = \(\dfrac{36}{90}\) 

Vì \(\dfrac{20}{90}\) < \(\dfrac{36}{90}\) vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

b; \(\dfrac{4}{9}\) = \(\dfrac{4\times10}{9\times10}\) = \(\dfrac{40}{90}\); \(\dfrac{6}{10}\) = \(\dfrac{6\times9}{10\times9}\) = \(\dfrac{54}{90}\)

   Vì \(\dfrac{40}{90}\) < \(\dfrac{54}{90}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{6}{10}\)

c; \(\dfrac{3}{8}\) = \(\dfrac{3\times7}{8\times7}\) = \(\dfrac{21}{56}\); \(\dfrac{4}{7}\) =  \(\dfrac{4\times8}{7\times8}\) = \(\dfrac{32}{56}\)

Vì \(\dfrac{21}{56}\) < \(\dfrac{32}{56}\) vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

d; \(\dfrac{5}{9}\) = \(\dfrac{5\times10}{9\times10}\) = \(\dfrac{50}{90}\); \(\dfrac{7}{10}\) = \(\dfrac{7\times9}{10\times9}\) = \(\dfrac{63}{90}\)

Vì \(\dfrac{50}{90}\) < \(\dfrac{63}{90}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\) 

   Cách ba:

a; \(\dfrac{2}{9}\) < \(\dfrac{2+2}{9+2}\) = \(\dfrac{4}{11}\) < \(\dfrac{4}{10}\) vậy \(\dfrac{2}{9}\) < \(\dfrac{4}{10}\)

b; \(\dfrac{4}{9}\) < \(\dfrac{4+2}{9+2}\) < \(\dfrac{6}{11}\) < \(\dfrac{6}{10}\) vậy \(\dfrac{4}{9}\) < \(\dfrac{6}{10}\)

c; \(\dfrac{3}{8}\) < \(\dfrac{3+1}{8+1}\) = \(\dfrac{4}{9}\) < \(\dfrac{4}{7}\) vậy \(\dfrac{3}{8}\) < \(\dfrac{4}{7}\)

d; \(\dfrac{5}{9}\) < \(\dfrac{5+2}{9+2}\) = \(\dfrac{7}{11}\) < \(\dfrac{7}{10}\) vậy \(\dfrac{5}{9}\) < \(\dfrac{7}{10}\)

Bài 1: 

a) \(\dfrac{-5}{6}\ne\dfrac{10}{-14}\left(\dfrac{10}{-14}=-\dfrac{5}{7}\right).\)

b) \(\dfrac{-15}{-60}\ne\dfrac{-3}{12}\left(\dfrac{-15}{-60}=\dfrac{1}{4}\right).\)

Bài 2:

a) \(\dfrac{20}{-140}=-\dfrac{1}{7}.\)

b) \(\dfrac{4.18}{9.12}=\dfrac{72}{108}=\dfrac{2}{3}.\)

c) \(\dfrac{17.25-17.3}{2.\left(-15\right)}=\dfrac{17.\left(25-3\right)}{-30}=-\dfrac{17.22}{30}=\dfrac{374}{30}=\dfrac{187}{15}.\)

Bài 3:

a) \(\dfrac{-3}{5}< \dfrac{4}{-7}.\)

b) \(\dfrac{-4}{21}>\dfrac{-7}{35}.\)

c) \(\dfrac{-7}{24}>\dfrac{-2}{3}.\)

d) \(\dfrac{-52}{167}< \dfrac{-3}{-4}.\)

Bài 1:

\(\dfrac{-5}{18}=\dfrac{-20}{72};\dfrac{7}{-24}=\dfrac{-21}{72}.\)

\(\dfrac{-15}{-40}=\dfrac{3}{8}=\dfrac{9}{24};\dfrac{24}{-72}=\dfrac{-1}{3}=\dfrac{-8}{24}.\)

Bài 3:

a) \(\dfrac{2}{3}h=\dfrac{8}{12}h;\dfrac{3}{4}h=\dfrac{9}{12}h.\Rightarrow\dfrac{2}{3}h< \dfrac{3}{4}h.\)

b) \(\dfrac{4}{5}km/h=\dfrac{8}{10}km/h;\dfrac{9}{10}km/h.\Rightarrow\dfrac{4}{5}km/h< \dfrac{9}{10}km/h.\)

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