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a/ \(\dfrac{7}{10}=\dfrac{7.15}{10.15}=\dfrac{105}{150}\)

\(\dfrac{11}{15}=\dfrac{11.10}{15.10}=\dfrac{110}{150}\)

-Vì \(\dfrac{105}{150}< \dfrac{110}{150}\)(105<110)nên \(\dfrac{7}{10}< \dfrac{11}{15}\)

b/ \(\dfrac{-1}{8}=\dfrac{-1.3}{8.3}=\dfrac{-3}{24}\)

-Vì \(\dfrac{-3}{24}>\dfrac{-5}{24}\left(-3>-5\right)\)nên\(\dfrac{-1}{8}>\dfrac{-5}{24}\)

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

\(\dfrac{10}{40}=\dfrac{10:10}{40:10}=\dfrac{1}{4}\)

-Vì \(\dfrac{1}{4}=\dfrac{1}{4}\)nên\(\dfrac{25}{100}=\dfrac{10}{40}\)

a/ \(\dfrac{7}{10}< \dfrac{11}{15}\)

c/ \(\dfrac{25}{100}=\dfrac{10}{40}\)

a) 

b) 

c) \(\dfrac{25}{100}=\dfrac{10}{40}\)

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=

\(\dfrac{7}{10}=\dfrac{70}{100}>\dfrac{43}{100};\dfrac{6}{10}=\dfrac{60}{100}< \dfrac{85}{100};\dfrac{7}{10}=\dfrac{70}{100}\)

\(\dfrac{7}{10}>\dfrac{43}{100};\dfrac{6}{10}< \dfrac{85}{100};\dfrac{7}{10}=\dfrac{70}{100}\)

Em quy đồng rồi so sánh

quy đồng rồi so sánh phân số nhá 

\(\dfrac{5}{6}< \dfrac{9}{10}>\dfrac{7}{8}\)

a)\(\dfrac{-8}{9}< \dfrac{-7}{9}\\ \dfrac{6}{7}< \dfrac{11}{10}\)

a) Vì -8<-7 nên \(\dfrac{-8}{9}< \dfrac{-7}{9}\)

b) Ta có: \(\dfrac{6}{7}< 1;\dfrac{11}{10}>1\)

nên \(\dfrac{6}{7}< \dfrac{11}{10}\)

Giải:

a) -8/9 < -7/9

b) Ta có: 6/7 = 60/70

                 11/10 = 77/70

Vì 60/70 < 77/70 nên :

    6/7 < 11/10

a)=

b)>

c)=

a) \(\dfrac{6}{14}=\dfrac{6:2}{14:2}=\dfrac{3}{7}\)

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

b) \(\dfrac{6}{15}=\dfrac{6:3}{15:3}=\dfrac{2}{5}\)

\(\dfrac{3}{5}>\dfrac{2}{5}\)

c) \(\dfrac{10}{18}=\dfrac{10:2}{18:2}=\dfrac{5}{9}\)

\(\dfrac{5}{9}>\dfrac{2}{9}\)

Ta có: \(\dfrac{6}{{15}} = \dfrac{{6:3}}{{15:3}} = \dfrac{2}{5}\)

\(\begin{array}{l}BCNN\left( {20,5} \right) = 20\\\dfrac{2}{5} = \dfrac{{2.4}}{{5.4}} = \dfrac{8}{{20}}\end{array}\)

Vì 3 < 8 nên \(\dfrac{3}{{20}} < \dfrac{8}{{20}}\)

Suy ra \(\dfrac{3}{{20}} < \dfrac{6}{{15}}\)

\(7A=\dfrac{7^{100}+14}{7^{100}+2}=1+\dfrac{12}{7^{100}+2}\)

\(7B=\dfrac{7^{99}+14}{7^{99}+2}=1+\dfrac{12}{7^{99}+2}\)

7^100+2>7^99+2

=>7A<7B

=>A<B