\(Từ\) \(\dfrac{-1,2}{1,6}=\dfrac{55}{-7\dfrac{1}{3}}\Rightarrow\) \(\dfrac{1,6}{-1,2}=\dfrac{-7\dfrac{1}{3}}{55}\)

\(\Rightarrow\dfrac{-7\dfrac{1}{3}}{55}=\dfrac{1,6}{-1,2}\)

\(\Rightarrow\dfrac{55}{-7\dfrac{1}{3}}=\dfrac{-1,2}{1,6}\)

1)

a) \(1\dfrac{5}{6}=\dfrac{-x}{5}\)

\(\Rightarrow\dfrac{11}{6}=\dfrac{-x}{5}\)

\(\Rightarrow-x=\dfrac{5.11}{6}=\dfrac{55}{6}\)

\(\Rightarrow x=-\dfrac{55}{6}\)

b) 4,25 : 8 = -3,5 : x

\(\dfrac{4,25}{8}=\dfrac{-3,5}{x}\)

\(x=\dfrac{-3,5.8}{4,25}\)

\(x=\dfrac{-28}{4,25}\)

2.

\(-\dfrac{12}{1,6}=\dfrac{55}{-7\dfrac{1}{3}}\)

\(\Rightarrow-\dfrac{12}{1,6}=\dfrac{55}{-\dfrac{22}{3}}\)

Ta có thể lặp đc các tỉ lệ thức sau:

\(-\dfrac{12}{1,6}=\dfrac{55}{-\dfrac{22}{3}}\)

\(\dfrac{-\dfrac{22}{3}}{1,6}=\dfrac{55}{-12}\)

\(-\dfrac{12}{55}=\dfrac{1,6}{-\dfrac{22}{3}}\)

\(\dfrac{1,6}{-12}=\dfrac{-\dfrac{22}{3}}{55}\)

https://hoc24.vn/hoi-dap/ti-le-thuc.4497/

\(\dfrac{-12}{1,6}=\dfrac{55}{-7\dfrac{1}{3}}\)

\(\Rightarrow\dfrac{-12}{-7\dfrac{1}{3}}=\dfrac{55}{1,6};\dfrac{-12}{55}=\dfrac{-7\dfrac{1}{3}}{1,6};\dfrac{1,6}{55}=\dfrac{-7\dfrac{1}{3}}{-12};\dfrac{1,6}{-7\dfrac{1}{3}}=\dfrac{55}{-12}\)

\(\dfrac{-12}{-7\dfrac{1}{3}}=\dfrac{55}{1.6};\dfrac{-12}{55}=\dfrac{-7\dfrac{1}{3}}{1.6};\dfrac{-7\dfrac{1}{3}}{-12}=\dfrac{1.6}{55};\dfrac{55}{-12}=\dfrac{1.6}{-7\dfrac{1}{3}}\)

-7 1/3 = -22/3

55/(-22/3) =  -15/2 = -7,5

====> -12/1,6 = 55/-7,5

======> 1,6/-12 = -7,5/55 ; 1,6/-7,5 = -12/55 ; -7,5/1,6 = 55/-12

( Mk gj hơi khó hỉu, moq pn pỏ wa nhé!! )