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12/49 > 13/47
64/85 > 73/81
19/31 > 17/35
67/77 > 73/83
a) 12 < 13; 49 > 47 => 12/49 < 13/47
b) 64 < 73; 85 > 81 => 64/85 < 73/81
c) 19 > 17; 31 < 35 => 19/31 > 17/35
d) 67/77 = 1 - 10/77; 73/83 = 1- 10/83. Mà 10/77 > 10/83 => 67/77 < 73/83.
e) 456/461 = 1 - 5/461; 123/128 = 1 - 5/128. Mà 5/461 < 5/128 => 456/461 > 123/128.
f) 149/157 = 1 - 8/157; 449/458 = 1 - 9/458. Mà 8/157 = 16/314 > 9/458 => 149/157 < 449/458.
\(\dfrac{12}{49}=\dfrac{564}{2303};\dfrac{13}{47}=\dfrac{637}{2303}\)
Vì 564<637=>\(\dfrac{564}{2303}< \dfrac{637}{2303}\)=>\(\dfrac{12}{49}< \dfrac{13}{47}\)
a)\(12< 13;49>47\)
\(\Rightarrow\dfrac{12}{49}< \dfrac{13}{47}\)
b)\(\dfrac{64}{85}>\dfrac{43}{85}\Rightarrow\dfrac{64}{85}>\dfrac{1}{2}\)
\(\dfrac{17}{35}< \dfrac{17}{34}\Rightarrow\dfrac{17}{35}< \dfrac{1}{2}\)
\(\Rightarrow\dfrac{17}{35}< \dfrac{64}{85}\)
c) \(\dfrac{19}{31}>\dfrac{16}{31}\Rightarrow\dfrac{19}{31}>\dfrac{1}{2}\)
\(\dfrac{17}{35}< \dfrac{17}{34}\Rightarrow\dfrac{17}{35}< \dfrac{1}{2}\)
\(\Rightarrow\dfrac{17}{35}< \dfrac{19}{31}\)
d)
\(1-\dfrac{67}{77}=\dfrac{10}{77}\)
\(1-\dfrac{73}{83}=\dfrac{10}{83}\)
\(\dfrac{10}{77}>\dfrac{10}{83}\Rightarrow\dfrac{67}{77}< \dfrac{73}{83}\)
e)\(1-\dfrac{456}{461}=\dfrac{5}{461}\)
\(1-\dfrac{123}{128}=\dfrac{5}{128}\)
\(\dfrac{5}{461}< \dfrac{5}{128}\Rightarrow\dfrac{456}{461}>\dfrac{123}{128}\)
\(a,\dfrac{12}{49}< \dfrac{12}{47}< \dfrac{13}{47}\Rightarrow\dfrac{12}{49}< \dfrac{12}{47}\)
b, Ta có: \(\dfrac{17}{35}=\dfrac{51}{105}\)
\(\dfrac{64}{85}>\dfrac{64}{105}>\dfrac{51}{105}\Rightarrow\dfrac{64}{85}>\dfrac{51}{105}\) hay \(\dfrac{64}{85}>\dfrac{17}{85}\)
c,\(\dfrac{19}{31}>\dfrac{17}{31}>\dfrac{17}{35}\Rightarrow\dfrac{19}{31}>\dfrac{17}{35}\)
d, \(\dfrac{67}{77}+\dfrac{10}{77}=1\)
\(\dfrac{73}{83}+\dfrac{10}{83}=1\)
\(\dfrac{10}{77}>\dfrac{10}{83}\Rightarrow\dfrac{67}{77}< \dfrac{73}{83}\)
e, \(\dfrac{456}{461}+\dfrac{5}{461}=1\)
\(\dfrac{123}{128}+\dfrac{5}{128}=1\)
\(\dfrac{5}{461}< \dfrac{5}{128}\Rightarrow\dfrac{456}{461}>\dfrac{123}{128}\)
a) Quy đồng mẫu số:
\(\frac{12}{49}=\frac{12.47}{49.47}=\frac{564}{2303}\)
\(\frac{13}{47}=\frac{13.49}{47.49}=\frac{637}{2303}\)
\(\Rightarrow\frac{564}{2303}< \frac{637}{2303}\left(564< 637\right)\)
hay \(\frac{12}{49}< \frac{13}{47}\)
b) Quy đồng mẫu số:
\(\frac{456}{461}=\frac{456.128}{461.128}=\frac{58368}{59008}\)
\(\frac{123}{128}=\frac{123.461}{128.461}=\frac{56703}{59008}\)
\(\Rightarrow\frac{58368}{59008}>\frac{56703}{59008}\left(58368>56703\right)\)
hay ;\(\frac{456}{461}>\frac{123}{128}\)
c) Quy đồng mẫu số:
\(\frac{64}{85}=\frac{64.81}{85.81}=\frac{5184}{6885}\)
\(\frac{73}{81}=\frac{73.85}{81.85}=\frac{6205}{6885}\)
..............
Đag mắc đi hc
a) Ta có: \(\frac{13}{21}=\frac{26}{42}\)
\(\frac{9}{14}=\frac{27}{42}\)
Vì \(\frac{26}{42}< \frac{27}{42}\) nên \(\frac{13}{21}< \frac{9}{14}\)
b) Ta có: \(\frac{7}{-12}=\frac{-21}{36}\)
\(\frac{11}{-18}=\frac{-22}{36}\)
Vì \(\frac{-21}{36}>\frac{-22}{36}\) nên \(\frac{7}{-12}>\frac{11}{-18}\)
c) Ta có: \(\frac{17}{58}=\frac{510}{1740}\)
\(\frac{13}{60}=\frac{377}{1740}\)
Vì \(\frac{510}{1740}>\frac{377}{1740}\) nên \(\frac{17}{58}>\frac{13}{60}\)
d) Ta có: \(\frac{-19}{33}=\frac{-703}{1221}\)
\(\frac{-17}{37}=\frac{-561}{1221}\)
Vì \(\frac{-703}{1221}< \frac{-561}{1221}\) nên \(\frac{-19}{33}< \frac{-17}{33}\)
e) Ta có: \(\frac{67}{77}=\frac{5561}{6391}\)
\(\frac{73}{83}=\frac{5621}{6391}\)
Vì \(\frac{5561}{6391}< \frac{5621}{6391}\) nên \(\frac{67}{77}< \frac{73}{83}\)
f) Ta có: \(\frac{-456}{461}=\frac{-58368}{59008}\)
\(\frac{-123}{128}=\frac{-56703}{59008}\)
Vì \(\frac{-58368}{59008}< \frac{-56703}{59008}\) nên \(\frac{-456}{461}< \frac{-123}{128}\)
