3/5

- 2/3

4/39

26/45

1/12

-29/21

Vì:

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

\(\dfrac{12}{14}=\dfrac{12:2}{14:2}=\dfrac{6}{7}\)

\(\dfrac{18}{21}=\dfrac{18:3}{21:3}=\dfrac{6}{7}\)

\(\dfrac{60}{100}=\dfrac{60:20}{100:20}=\dfrac{3}{5}\)

Vậy \(\dfrac{3}{5}=\dfrac{12}{20}=\dfrac{60}{100}\)            ;                 \(\dfrac{6}{7}=\dfrac{12}{14}=\dfrac{18}{21}\)

\(#Wendy.Dang\)

\(\dfrac{18}{21}=\dfrac{6}{7}\)=\(\dfrac{12}{14}=\dfrac{36}{42}\)=\(\dfrac{90}{150}=\dfrac{3}{5}\)=\(\dfrac{12}{20}=\dfrac{60}{100}=\dfrac{21}{35}\)

\(\dfrac{18}{21}=\dfrac{12}{14}=\dfrac{6}{7}=\dfrac{36}{42}\)

\(\dfrac{90}{150}=\dfrac{12}{20}=\dfrac{60}{100}=\dfrac{3}{5}=\dfrac{21}{35}\)

Trả lời:

Phân số tối giản là: 11/13;7/18

hoc tốt 

14/21

Phân số tối giản là: \(\frac{11}{13}\); \(\frac{7}{18}\)

hok tốt!!

\(\frac{6}{8}+\frac{-14}{21}=\frac{1}{12}\)

\(\frac{6}{18}+\frac{-14}{21}=\frac{42}{126}+\frac{-84}{126}=\frac{-42}{126}=\frac{-1}{3}\)

+Rút gọn:\(\frac{6}{18}=\frac{6:6}{18:6}=\frac{1}{3};\frac{-14}{21}=\frac{-14:7}{21:7}=\frac{-2}{3}\)

Ta có \(\frac{1}{3}+\frac{-2}{3}=\frac{1+\left(-2\right)}{3}=\frac{-1}{3}\)

Vậy \(\frac{6}{18}+\frac{-14}{21}=\frac{-1}{3}\)

^{_{\(\dfrac{5}{7}=\dfrac{15}{21};\dfrac{6}{8}=\dfrac{3}{4};\dfrac{8}{9}=\dfrac{16}{18};\dfrac{12}{16}=\dfrac{18}{24}\)}}

\(\dfrac{5}{7}=\dfrac{15}{21};\dfrac{6}{8}=\dfrac{18}{24};\dfrac{8}{9}=\dfrac{16}{18};\dfrac{3}{4}=\dfrac{12}{16}\)

5/7=15/21;6/8=3/4;8/9=16/18;12/16=18/24

B, -2/3+4/7=-2/21