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![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{1}{2}và\dfrac{2}{9}\)
\(\dfrac{1}{2}=\dfrac{1.9}{2.9}=\dfrac{9}{18};\dfrac{2}{9}=\dfrac{2.2}{9.2}=\dfrac{4}{18}\)
\(\dfrac{3}{5}và\dfrac{9}{8}\)
\(\dfrac{3}{5}=\dfrac{3.8}{5.8}=\dfrac{24}{40};\dfrac{9}{8}=\dfrac{9.5}{8.5}=\dfrac{45}{40}\)
\(\dfrac{5}{6}và\dfrac{4}{9}\)
\(\dfrac{5}{6}=\dfrac{5.3}{6.3}=\dfrac{15}{18};\dfrac{4}{9}=\dfrac{4.2}{9.2}=\dfrac{8}{18}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
bài3
1. \(\frac{4}{3}\)= \(\frac{4x4}{3x4}\)=\(\frac{20}{12}\)
\(\frac{3}{4}\)=\(\frac{3x3}{4x3}\)=\(\frac{9}{12}\)
2.\(\frac{5}{4}\)=\(\frac{5x6}{4x6}\)=\(\frac{30}{24}\)
\(\frac{5}{6}\)=\(\frac{5x4}{6x4}\)=\(\frac{20}{24}\)
3.\(\frac{3}{8}\)=\(\frac{3x6}{8x6}\)=\(\frac{18}{48}\)
\(\frac{1}{6}\)=\(\frac{1x6}{6x8}\)=\(\frac{6}{48}\)
4.\(\frac{2}{5}\)=\(\frac{2x7}{5x7}\)=\(\frac{14}{35}\)
\(\frac{4}{7}\)=\(\frac{4x5}{7x5}\)=\(\frac{20}{35}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 7/5 và 1/6
Ta có : 7/5 = \(\frac{7\times6}{5\times6}=\frac{42}{30}\) Và : \(\frac{1\times5}{6\times5}=\frac{5}{30}\)
b) 4/3 và 7/2
Ta có : \(\frac{4}{3}=\frac{4\times2}{3\times2}=\frac{8}{6}\)và \(\frac{7}{2}=\frac{7\times3}{2\times3}=\frac{21}{6}\)
v) 3/4 và 2/5
Ta có : \(\frac{3}{4}=\frac{3\times5}{4\times5}=\frac{15}{20}\)và \(\frac{2}{5}=\frac{2\times4}{5\times4}=\frac{8}{20}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a: 5/4<7/4
b: 2/3=34/51
9/17=27/51
mà 34>27
nên 2/3>9/17
Bài 3:
a: 1/3+3/8=8/24+9/24=17/24
b: 7/6+5/18=21/18+5/18=26/18=13/9
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{2}{5}=\dfrac{4}{10}\)
\(\dfrac{4}{10}>\dfrac{3}{10}\)
b) \(\dfrac{5}{6}=\dfrac{10}{12}\)
\(\dfrac{7}{12}< \dfrac{10}{12}\)
c) \(\dfrac{1}{2}=\dfrac{2}{4}\)
\(\dfrac{3}{4}< \dfrac{2}{4}\)
d) \(\dfrac{8}{3}=\dfrac{56}{21}\)
\(\dfrac{56}{21}>\dfrac{11}{21}\)
B
B