\(\frac{18}{7}:9=\frac{18}{7}:\frac{9}{1}=\frac{18}{7}×\frac{1}{9}=\frac{9×2×1}{7×9}=\frac{2}{7}\)

\(\frac{64}{35}:4=\frac{64}{35}:\frac{4}{1}=\frac{64}{35}×\frac{1}{4}=\frac{16×4×1}{35×4}=\frac{16}{35}\)

\(\frac{24}{11}:12=\frac{24}{11}:\frac{12}{1}=\frac{24}{11}×\frac{1}{12}=\frac{12×2×1}{11×12}=\frac{2}{11}\)

\(\frac{35}{14}:5=\frac{35}{14}:\frac{5}{1}=\frac{35}{14}×\frac{1}{5}=\frac{5×7×1}{14×5}=\frac{7}{14}=\frac{1}{2}\)

18/17:9=18/17:9/1=18/17x1/9=2/17

64/35:4=64/35:4/1=64/35x1/4=16/35

24/11:12=24/11:12/1=24/11x1/12=2/11

35/4:5=35/4:5/1=35/4x1/5=7/4

a: =(-5-5)/9=-10/9

b: =1/4+1/5=9/20

c: =-11/2+2/2=-9/2

a)-10/9

b)9/20

c)-9/2

sai thì sorry

a) \(\dfrac{-5}{9}-\dfrac{5}{9}=\dfrac{\left(-5\right)-5}{9}=\dfrac{-\left(5+5\right)}{9}=\dfrac{-10}{9}\)

b) \(\dfrac{9}{36}-\dfrac{7}{-35}=\dfrac{1}{4}+\dfrac{1}{-5}=\dfrac{9}{-20}\)

c) \(\dfrac{-11}{2}-\left(-1\right)=\dfrac{-11}{2}+\dfrac{2}{2}=\dfrac{9}{2}\)

Sách giáo khoa 4 nha các bn !!!

Trả lời đúng mik **** cho !!!

B nhé 

HT

Chọn B nha bạn

B. 

Bài 1: 

Các phân số 3/5; 9/20; 17/27 là phân số tối giản

Bài 2: 

a: 1/4=7/28

3/7=12/28

b: 4/5=28/35

17/35=17/35

c: 4/9=28/63

8/21=24/63

d: 5/6=20/24

7/8=21/24

ngu dốt

3/5+9/35

=21/35+9/35

=30/35

=6/7

\(3/5+9/35=21/35+9/35=30/35=6/7\) nhé

\(\dfrac{3}{5}+\dfrac{9}{35}=\dfrac{21}{35}+\dfrac{9}{35}=\dfrac{30}{35}\)\(=\dfrac{6}{7}\)

=\(\dfrac{1}{6}\)

\(\dfrac{1}{6}\)

^{_{\(\dfrac{1}{6}\)}}