a 

oki

a : vì \(\dfrac{354}{758}< 1;\dfrac{123}{56}>1\\ \Rightarrow\dfrac{354}{758}< \dfrac{123}{56}\)

b:\(\dfrac{-18}{2021}< 0;\dfrac{75}{2022}>0\\ \Rightarrow\dfrac{-18}{2021}< \dfrac{75}{2022}\)

a)  Do 354/758<1 ;123/56>1

=>354/758<123/56

b) -18/2021<0;72/2022>0

=>-18/2021<72/2022

_{Làm ơn giúp mình với !}

\(\dfrac{12}{19}< \dfrac{23}{25}\)

\(\dfrac{21}{27}< \dfrac{23}{25}\)

\(\dfrac{12}{19}< \dfrac{23}{25};\dfrac{21}{27}< \dfrac{23}{25}\)

a) \(\dfrac{12}{19}=\dfrac{19}{19}-\dfrac{7}{19}=1-\dfrac{7}{19}\)

\(\dfrac{23}{25}=\dfrac{25}{25}-\dfrac{2}{25}=1-\dfrac{2}{25}\).

-So sánh: \(\dfrac{7}{19}\) và \(\dfrac{2}{25}\).

\(\dfrac{7}{19}=\dfrac{14}{38};\dfrac{2}{25}=\dfrac{14}{175}\Rightarrow\dfrac{7}{19}>\dfrac{2}{25}\left(\dfrac{14}{38}>\dfrac{14}{175}\right)\)

\(\Rightarrow1-\dfrac{7}{19}< 1-\dfrac{2}{25}\) 

\(\Rightarrow\dfrac{12}{19}< \dfrac{23}{25}\)

-Câu b làm tương tự bạn nhé.

hai phân số nào em nhở?

và phân số nào nữa?

b)21/27<21/25<23/25

Ta có: \(\frac{14}{21}< \frac{20}{21}\)

Mà  \(\frac{20}{21}< \frac{20}{31}\)

Nên \(\frac{14}{21}< \frac{20}{31}\)

a)  3 4 = 6 8 < 6 7

b)  17 − 21 = 51 − 63 > 51 − 31

5/4 > 2021/2022

vì 5/4 >1

2021/2022<1

ta có: \(\dfrac{2021}{2022}< 1\)

          \(\dfrac{5}{4}>1\)

\(\Rightarrow\dfrac{2021}{2022}< 1< \dfrac{5}{4}\)

vậy \(\dfrac{2021}{2022}< \dfrac{5}{4}\)

\(\dfrac{2021}{2022}< 1< \dfrac{5}{4}\)

A) Ta có: 

\(\dfrac{12}{13}=\dfrac{13}{13}-\dfrac{1}{13}=1-\dfrac{1}{13}\)

\(\dfrac{13}{14}=\dfrac{14}{14}-\dfrac{1}{14}=1-\dfrac{1}{14}\)

Mà \(1-\dfrac{1}{13}< -\dfrac{1}{14}\)

\(\Rightarrow\dfrac{12}{13}< \dfrac{13}{14}\)

B) Ta có:

\(\dfrac{125}{251}=\dfrac{251}{251}-\dfrac{126}{251}=1-\dfrac{126}{251}\)

\(\dfrac{127}{253}=\dfrac{253}{253}-\dfrac{126}{253}=1-\dfrac{126}{253}\)

Mà: \(1-\dfrac{126}{251}< 1-\dfrac{126}{253}\)

\(\Rightarrow\dfrac{125}{251}< \dfrac{127}{253}\)