Rút gọn :
10/15=2/3 ; 12/16=3/4 
Quy đồng : 
2/3 = 8/12 
3/4=9/12

\(a,\dfrac{3}{9}=\dfrac{1}{3}\\ \dfrac{16 }{24}=\dfrac{2}{3}\\ b,\dfrac{17}{51}=\dfrac{1}{3}=\dfrac{5}{15}\\ \dfrac{18}{90}=\dfrac{1}{5}=\dfrac{3}{15}\\ c,\dfrac{5}{10}=\dfrac{1}{2}=\dfrac{3}{6}\\ \dfrac{15}{45}=\dfrac{1}{3}=\dfrac{2}{6}\\ d,\dfrac{42}{63}=\dfrac{2}{3}=\dfrac{6}{9}\\ \dfrac{64}{72}=\dfrac{8}{9}\)

\(\frac{10}{15}=\frac{2}{3}\)\(\frac{2}{3}=\frac{2\times4}{3\times4}=\frac{8}{12}\)

\(\frac{12}{16}=\frac{3}{4}\)\(\frac{3}{4}=\frac{3\times3}{4\times3}=\frac{9}{12}\)

10/15=2/3=8/12

12/16=3/4=9/12

Ta có rút gọn hai phân số :

\(\frac{10}{15}=\frac{10:5}{15:5}=\frac{2}{3}\) và \(\frac{12}{16}=\frac{12:4}{16:4}=\frac{3}{4}\)

Quy đồng hai phân số mới , lấy mẫu số là : 3 x 4 = 12

Vậy mẫu số là 12

\(\frac{2}{3}=\frac{2\times4}{3\times4}=\frac{8}{12}\) và \(\frac{3}{4}=\frac{3\times3}{4\times3}=\frac{9}{12}\)

phân số của bạn đâu?

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

 cảm ơn chị ạ

Đáp án cần chọn là: B

9.8 − 7.18 3 2 .10 = 9.8 − 7.9.2 9.10 = 8 − 14 10 = − 3 5 16   .19 − 26   .   19 57   .   3 − 19 = 16   .19 − 26   .   19 19.3   .   3 − 19 = 16 − 26 9 − 1 = − 5 4

MSC = 20

− 3 5 = − 3.4 5.4 = − 12 20 ;     − 5 4 = − 5.5 4.5 = − 25 20

Vậy sau khi quy đồng ta được hai phân số:    − 12 20 và  − 25 20 .

a/\(\dfrac{15}{12}=\dfrac{15:3}{12:3}=\dfrac{5}{4}\)
\(\dfrac{27}{6}=\dfrac{27:3}{6:3}=\dfrac{9}{2}=\dfrac{9\times2}{2\times2}=\dfrac{18}{4}\)
b/\(\dfrac{10}{28}=\dfrac{10:2}{28:2}=\dfrac{5}{14}\)
\(\dfrac{40}{7}=\dfrac{40\times2}{7\times2}=\dfrac{80}{14}\)
c/\(\dfrac{14}{60}=\dfrac{7}{30}\)
\(\dfrac{4}{15}=\dfrac{4\times2}{15\times2}=\dfrac{8}{30}\)
#kễnh