Bài 1:

a. $\frac{15}{17}$ - $\frac{9}{17}$ = $\frac{15-9}{17}$ = $\frac{6}{17}$ 

$\frac{8}{7}$ - $\frac{5}{7}$ = $\frac{8-5}{7}$ = $\frac{3}{7}$ 

b;c: tự làm

Bài 2:

a. ; c. : tự làm

b. $\frac{2}{3}$ - $\frac{1}{2}$ = $\frac{4}{6}$ - $\frac{3}{6}$ = $\frac{4-3}{6}$ = $\frac{1}{6}$ 

$\frac{4}{3}$ - $\frac{2}{4}$ = $\frac{16}{12}$ - $\frac{6}{12}$ = $\frac{16-6}{12}$ = $\frac{10}{12}$ = $\frac{5}{6}$.

Bài 3:

$\frac{5}{8}$ + $\frac{4}{3}$ = $\frac{15}{24}$ + $\frac{32}{24}$ = $\frac{47}{24}$ 

$\frac{5}{7}$ - $\frac{2}{5}$ = $\frac{25}{35}$ - $\frac{14}{35}$ = $\frac{11}{35}$ 

$\frac{2}{5}$ + $\frac{5}{9}$ = $\frac{18}{45}$ + $\frac{25}{45}$ = $\frac{43}{45}$ 

$\frac{2}{3}$ - $\frac{4}{7}$ = $\frac{14}{21}$ - $\frac{12}{21}$ = $\frac{2}{21}$ 

Bài 4:

$\frac{3}{4}$ + $\frac{7}{12}$ = $\frac{9}{12}$ + $\frac{7}{12}$ = $\frac{16}{12}$ = $\frac{4}{3}$ 

$\frac{7}{4}$ - $\frac{7}{8}$ = $\frac{14}{8}$ - $\frac{7}{8}$ = $\frac{7}{8}$ 

$\frac{2}{7}$ + 4 = $\frac{2}{7}$ + $\frac{4}{1}$ =$\frac{2}{7}$ +  $\frac{28}{7}$ = $\frac{30}{7}$

3 - $\frac{4}{5}$ = $\frac{3}{1}$ - $\frac{4}{5}$ = $\frac{15}{5}$ - $\frac{4}{5}$ = $\frac{11}{5}$

Bài 5:

$\frac{7}{8}$ - $\frac{5}{8}$ = $\frac{2}{8}$ = $\frac{1}{4}$

$\frac{5}{6}$ - $\frac{2}{3}$  = $\frac{5}{6}$ - $\frac{4}{6}$ = $\frac{1}{6}$

$\frac{3}{5}$ - $\frac{1}{4}$  = $\frac{12}{20}$ - $\frac{5}{20}$ = $\frac{7}{20}$

$\frac{25}{21}$ - $\frac{6}{7}$ = $\frac{25}{21}$ - $\frac{18}{21}$ = $\frac{7}{21}$ = $\frac{1}{3}$ .

#_Kaiz_

Đáp án:

Giải thích các bước giải:

1,`15/17-9/17`

`=8/17`

`8/7-5/7`

`=3/7`

2,`2/3-1/2`

`=4/6-3/6`

`=1/6`

`4/3-2/4`

`=16/12-6/12`

`=10/12=5/6 `

`5/8+4/3=47/24`

`2/5+5/9=43/45`

`5/7-2/5=11/35`

`2/3-4/7=2/21`

4,

`3/4+7/12=16/12=4/3`

`2/7+4=30/7`

`7/4-7/8=7/8`

`3-4/5=11/5`

5,

`7/8-5/8=3/8`

`3/5-1/4=7/20`

`5/6-2/3=1/6`

`25/21-6/7=7/21=1/3`