_ \(\frac{7}{9}=\frac{7\times11}{9\times11}=\frac{7\times111}{9\times111}\Rightarrow\frac{7}{9}=\frac{77}{99}=\frac{777}{999}\)
_   \(\frac{13}{15}=\frac{13\times101}{15\times101}=\frac{13\times10101}{15\times10101}\Rightarrow\frac{13}{15}=\frac{1313}{1515}=\frac{131313}{151515}\)
_  \(\frac{20172017}{20072007}=\frac{20172017:10001}{20072007:10001}\Rightarrow\frac{20172017}{20072007}=\frac{2017}{2007}\)
_  \(\frac{123123}{456456}=\frac{123123:1001}{456456:1001}\Rightarrow\frac{123123}{456456}=\frac{123}{456}\)
~ Ủng hộ mk nha!~

theo mình là bằng nhau

Khó quá  

Khó quá 

vì 3 số chia hết cho nhau :

nếu 1313:13 =101 thì 1313:101=13 ( Vậy 13=13)

nếu 131313:13=10101 thì 131313:10101=13 (Vậy 13=13)

         Suy ra 3 số bằng nhau

về sau tăng gấpđôi số đầu

77/99=77:11/99:11=7/9

777/999=777:111/999:111=7/9

Vậy 7/9=77/99=777/999

77/99=77:11/99:11=7/9

777/999=777:111/999:111=7/9

Vậy 7/9=77/99=777/999

\(\dfrac{7}{9}=\dfrac{7}{9}\)

\(\dfrac{77}{99}=\dfrac{77\div11}{99\div11}=\dfrac{7}{9}\)

\(\dfrac{777}{999}=\dfrac{777\div111}{999\div111}=\dfrac{7}{9}\)

\(\dfrac{7777}{9999}=\dfrac{7777\div1111}{9999\div1111}=\dfrac{7}{9}\)

\(\Rightarrow\dfrac{7}{9}=\dfrac{77}{99}=\dfrac{777}{999}=\dfrac{7777}{9999}\)

\(\dfrac{77}{99}\) = \(\dfrac{77:11}{99:11}\) = \(\dfrac{7}{9}\)

\(\dfrac{777}{999}\) = \(\dfrac{777:111}{999:111}\) = \(\dfrac{7}{9}\)

\(\dfrac{7777}{9999}\) = \(\dfrac{7777:1111}{9999:1111}\) = \(\dfrac{7}{9}\)

Từ những lập luận luận trên ta có:

\(\dfrac{7}{9}\) = \(\dfrac{77}{99}\) = \(\dfrac{777}{999}\) = \(\dfrac{7777}{9999}\) (đpcm)

Bài này chỉ cần rút gọn phân số thứ 2 thôi là ra.

a) \(\frac{143}{363}=\frac{13}{33}\)

 \(\Rightarrow\frac{13}{33}=\frac{13}{33}\)

Vậy: \(\frac{13}{33}=\frac{143}{363}\)

b) \(\frac{1212}{2727}=\frac{12}{27}\)(Cái này chưa phải tối giản nhưng rút gọn vậy đủ dùng rồi!)

\(\Rightarrow\frac{12}{27}=\frac{12}{27}\)

Vậy: \(\frac{12}{27}=\frac{1212}{2727}\)

A/ \(\frac{143}{363}=\frac{11.13}{11.33}=\frac{13}{33}\)=> ĐPCM

B/ \(\frac{1212}{2727}=\frac{101.12}{101.27}=\frac{12}{27}\)=> ĐPCM

\(39+\dfrac{13}{84}+57=\dfrac{8077}{84}\)

\(78+\dfrac{26}{168}+114=\dfrac{16141}{84}\)

a)\(\frac{143}{363}=\frac{13.11}{33.11}=\frac{13}{33}\)\(\Rightarrow\frac{13}{33}=\frac{143}{363}\)

b)\(\frac{1212}{2727}=\frac{12.101}{27.101}=\frac{12}{27}\Rightarrow\frac{12}{27}=\frac{1212}{2727}\)

Ta có công thức tổng quát:\(\frac{abab}{bcbc}=\frac{ab}{bc}\)