a) Không

b) Không

a 1,75 * 34= 2 * 29,75
   1,75/2 = 29,75/34    34/2 = 29,75/1,75   1,75/29,75 = 2/34    1,75/2 = 29,75/34
    chúc bạn học tốt

a) 9 . 12 = 4 . 27

\(\Rightarrow\text{ }\frac{9}{4}=\frac{27}{12}\); \(\frac{9}{27}=\frac{4}{12}\); \(\frac{12}{4}=\frac{27}{9}\); \(\frac{12}{27}=\frac{4}{9}\)

b) 4,8,16,32

\(\Rightarrow\text{ }\text{ }4.32=8.16\)

\(\Rightarrow\text{ }\frac{4}{8}=\frac{16}{32}\); \(\frac{4}{16}=\frac{8}{32}\); \(\frac{32}{8}=\frac{16}{4}\); \(\frac{32}{16}=\frac{8}{4}\)

Các tỉ lệ thức có thể lập được:

\(\dfrac{4,5}{9}=\dfrac{3,7}{7,4};\dfrac{9}{4,5}=\dfrac{7,4}{3,7};\dfrac{3,7}{4,5}=\dfrac{7,4}{9};\dfrac{4,5}{3,7}=\dfrac{9}{7,4}\)

a, vì  1.16 = 2.8

Vậy ta có các tỉ lệ thức: \(\dfrac{1}{2}\) = \(\dfrac{8}{16}\); \(\dfrac{1}{8}\) = \(\dfrac{2}{16}\); \(\dfrac{2}{1}\) = \(\dfrac{16}{8}\); \(\dfrac{16}{2}\) = \(\dfrac{8}{1}\)

b, \(\dfrac{3}{2}\) : \(\dfrac{2}{3}\) = \(\dfrac{1}{4}\) : \(\dfrac{1}{9}\) ⇒ \(\dfrac{3}{2}\).\(\dfrac{1}{9}\) = \(\dfrac{1}{4}\).\(\dfrac{2}{3}\)

     \(\dfrac{3}{2}\) : \(\dfrac{1}{4}\) = \(\dfrac{2}{3}\)  : \(\dfrac{1}{9}\)

      \(\dfrac{1}{9}\) :  \(\dfrac{1}{4}\) = \(\dfrac{2}{3}\) : \(\dfrac{3}{2}\)

      \(\dfrac{1}{9}\) : \(\dfrac{2}{3}\) = \(\dfrac{1}{4}\) : \(\dfrac{3}{2}\) 

\(\left(-4\right)\cdot\left(-15\right)=12\cdot5\)

Suy ra: \(\dfrac{-4}{12}=\dfrac{5}{-15};\dfrac{-4}{5}=\dfrac{12}{-15};\dfrac{12}{-4}=\dfrac{-15}{5};\dfrac{5}{-4}=\dfrac{-15}{12}\)

\(\dfrac{-4}{12}=\dfrac{5}{-15}\\ \dfrac{-4}{5}=\dfrac{12}{-15}\)