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

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

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

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

\(\dfrac{2}{4}=\dfrac{8}{16};\dfrac{4}{2}=\dfrac{16}{8};\dfrac{4}{16}=\dfrac{2}{8};\dfrac{16}{4}=\dfrac{8}{2}\)

2/8=4/16

8/2=16/4

2/4=8/16

4/2=16/8

a nhân b=c nhân d. a,d là ngoại tỉ, b và c là trung tỉ

\(1.\)

\(a,\)

\(7.\left(-28\right)=\left(-49\right).4\)

Ta có :   \(\frac{7}{-49}=\frac{4}{-28}\)                                                     \(\frac{-28}{4}=\frac{-49}{7}\)

                 \(\frac{7}{4}=\frac{-49}{-28}\)                                                      \(\frac{-28}{-49}=\frac{4}{7}\)

\(b,\)

\(0,36.4,25=0,9.1,7\)

Ta có :   \(\frac{0,36}{0,9}=\frac{1,7}{4,25}\)                                                        \(\frac{0,36}{1,7}=\frac{0,9}{4,25}\)

              \(\frac{4,25}{0,9}=\frac{1,7}{0,36}\)                                                        \(\frac{4,25}{1,7}=\frac{0,9}{0,36}\)

a: \(\dfrac{1.12}{2.8}=\dfrac{-4}{-10};\dfrac{1.12}{-4}=\dfrac{2.8}{-10};\dfrac{2.8}{1.12}=\dfrac{-10}{-4};\dfrac{-4}{1.12}=\dfrac{-10}{2.8}\)

b: \(\dfrac{0.16}{0.4}=\dfrac{0.32}{0.8};\dfrac{0.16}{0.32}=\dfrac{0.4}{0.8};\dfrac{0.4}{0.16}=\dfrac{0.8}{0.32};\dfrac{0.32}{0.16}=\dfrac{0.8}{0.4}\)