Bài `1` `:`

`a,` `8/7` `=` $\dfrac{8 \times 8}{7 \times 8}$ `=` `64/56`

`7/8` `=` $\dfrac{7 \times 7}{8 \times 7}$ `=` `49/56`

`b,` `4/9` `=` $\dfrac{4 \times 4}{9 \times 4}$ `=` `16/36`

`c,` `4/7` `=` $\dfrac{4 \times 2}{7 \times 2}$ `=` `8/14`

`d,` `4/6` `=` $\dfrac{4 \times 2}{6 \times 2}$ `=` `8/12`

`7/2` `=` $\dfrac{7 \times 7}{2 \times 6}$ `=` `49/12`

Bài `3` `:`

`a,` `3/5` `=` $\dfrac{3 \times 3}{5 \times 3}$ `=` `9/15`

`->` `6/15` `<` `9/15`

`->` `6/15` `<` `3/5`

Vậy ...

`b,` `3/4` `=` $\dfrac{3 \times 6}{4 \times 6}$ `=` `18/24`

`->` `18/24` `=` `18/24`

`->` `18/24` `=` `3/4`

Vậy ...

`c,` `2/7` `=` $\dfrac{2 \times 5}{7 \times 5}$ `=` `10/35`

`->` `14/35` `>` `10/35`

`->` `14/35` `>` `2/7`

Vậy ...

`d,` `2/9` `=` $\dfrac{2 \times 4}{9 \times 4}$ `=` `8/36`

`->` `8/36` `>` `1/36`

`->` `2/9` `>` `1/36`

Vậy ...