2/5

4/9

2/5

2/3

rút gọn phân số :
12/30 =2/5
20/45= 4/9
28/70=2/5
34/51 =2/3

\(a,\\ =\dfrac{5}{4}-\dfrac{3}{4}=\dfrac{2}{4}=\dfrac{1}{2}\\ b,\\ =\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{10-6}{15}=\dfrac{4}{15}\\ c,\\ =\dfrac{5}{6}-\dfrac{1}{4}=\dfrac{20-6}{24}=\dfrac{14}{24}=\dfrac{7}{12}\\ d,\\ =\dfrac{4}{3}-\dfrac{1}{4}=\dfrac{12-3}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

 cảm ơn chị ạ

Rút gọn các phân số sau về phân số tối giản:
12/30 ................\(=\dfrac{12:6}{30:6}=\dfrac{2}{5}\)...........................................

20/45 ....................\(=\dfrac{20:5}{45:5}=\dfrac{4}{9}\)......................................

28/70.....................\(=\dfrac{28:14}{70:14}=\dfrac{2}{5}\).......................................

Rút gọn các phân số sau về phân số tối giản:
12/30 ..= 6/15........................................................

20/45 ..=4/9........................................................

28/70..=14/5..........................................................

34/51..=2/3..........................................................

215/300..=43/20.....................................................

1200/2010..=120/201.................................................

= =8/5

Ta có: \(-\frac{72}{45}=\frac{-72:9}{45:9}=\frac{-8}{5}\)

4/9 k mik nha chia cho 5 đó bn

\(\frac{4}{9}\)

20/45 = 4/9

14/35 = 2/7

-32/44 = -8/11

Chúc bạn học tốt !!!  :)))

Đáp án : 

\(\frac{20}{45}=\frac{20:5}{45:5}=\frac{4}{9}\)

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

\(\frac{-32}{44}=\frac{-32:4}{44:4}=\frac{-8}{11}\)

Hok tốt

\(\frac{15}{30}=\frac{15:15}{30:15}=\frac{1}{2}\)

\(\frac{20}{25}=\frac{20:5}{25:5}=\frac{4}{5}\)

\(\frac{18}{18}=1\)

\(\frac{25}{45}=\frac{25:5}{45:5}=\frac{5}{9}\)

\(\frac{15}{30}=\frac{1}{2}\)

\(\frac{20}{25}=\frac{4}{5}\)

\(\frac{18}{18}=1\)

\(\frac{25}{45}=\frac{5}{9}\)

\(\dfrac{45}{63}=\dfrac{9\text{×}5}{9\text{×}7}=\dfrac{5}{7}\)

\(\dfrac{45}{63}=\dfrac{45:9}{63:9}=\dfrac{5}{7}\)

\(\dfrac{-18}{45}=-\dfrac{2}{5}\)

\(\dfrac{-18}{45}=\dfrac{-18:9}{45:9}=\dfrac{-2}{5}\)