\(A=\dfrac{1+2+...+9}{11+12+...+19}=\dfrac{\left(9+1\right)\times9:2}{\left(19+11\right)\times9:2}=\dfrac{45}{135}=\dfrac{1}{3}\)

\(\dfrac{63}{27}=\dfrac{7}{3}\)

\(\dfrac{3\times4\times6}{12\times8\times5}=\dfrac{3\times1\times1}{1\times1\times5}=\dfrac{3}{5}\)

5/4 nha

5/4

5/4

143/132=1,083

3535/3737=0,945

ko dư nha

\(\frac{143}{132}=\frac{13}{12}\)

\(\frac{3535}{3737}=\frac{35}{37}\)

\(\dfrac{60}{75}\)=\(\dfrac{4}{5}\)

\(\dfrac{48}{72}\)=\(\dfrac{2}{3}\)

\(\dfrac{65}{9}\)=\(\dfrac{65}{9}\)

\(\dfrac{121212}{121212}\)=1

\(\dfrac{12\times1}{12\times6}=\dfrac{1}{6}\)

\(\dfrac{12}{72}=\dfrac{12:12}{72:12}=\dfrac{1}{6}\)

\(\dfrac{12}{72}=\dfrac{12:12}{72:12}=\dfrac{1}{6}\)

3/5

\(\dfrac{12}{20}=\dfrac{12:4}{20:4}=\dfrac{3}{5}\)

12/20=3/5

1: Rút gọn

a) \(-\dfrac{33}{51}=\dfrac{-33:3}{51:3}=\dfrac{-11}{17}\)

b) \(\dfrac{156}{-168}=\dfrac{-156}{168}=\dfrac{-156:12}{168:12}=\dfrac{-13}{14}\)

c) \(\dfrac{-75}{-100}=\dfrac{75}{100}=\dfrac{75:25}{100:25}=\dfrac{3}{4}\)

2: Quy đồng mẫu:

a) \(-\dfrac{3}{8}\) và \(\dfrac{5}{4}\)

MSC: 8

\(-\dfrac{3}{8}=\dfrac{-3}{8}\)

\(\dfrac{5}{4}=\dfrac{5\cdot2}{4\cdot2}=\dfrac{10}{8}\)

b) \(\dfrac{-7}{6}\) ; \(\dfrac{5}{12}\) và \(-\dfrac{5}{6}\)

MSC: 12

\(-\dfrac{7}{6}=\dfrac{-7\cdot2}{6\cdot2}=\dfrac{-14}{12}\)

\(\dfrac{5}{12}=\dfrac{5}{12}\)

\(\dfrac{-5}{6}=\dfrac{-5\cdot2}{6\cdot2}=\dfrac{-10}{12}\)

-8/12= -2/3

15/-60= 1/-4

-16/-72= 2/9

35/14.15= 1/6

-8/12 rút gọn bằng-2/3; 15/-60 =-1/4; -16/-72=2/9;35/14.15=1/6

-2/3

1/-4

2-9

1/6