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

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

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

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

\(14\cdot5=56\cdot1.25\)

\(\Leftrightarrow\dfrac{14}{56}=\dfrac{1.25}{5};\dfrac{14}{1.25}=\dfrac{56}{5};\dfrac{56}{14}=\dfrac{5}{1.25};\dfrac{1.25}{14}=\dfrac{5}{56}\)

\(1.25\cdot56=5\cdot14\)

\(\Leftrightarrow\dfrac{1.25}{5}=\dfrac{14}{56};\dfrac{1.25}{14}=\dfrac{5}{56};\dfrac{5}{1.25}=\dfrac{56}{14};\dfrac{14}{1.25}=\dfrac{56}{5}\)

đó là 

81/9=243/27      27/3=81/9        9/81=243/27       3/9=81/243     3/27=9/81       9/7=81/243          3/81=9/243        243/9=81/3      

3/9=27/81         27/9=243/81         9/3=81/27        9/3=243/81       243/9=81/3       81/9=27/3         

Có thể  và tỉ lệ thức đó là:

 \(\frac{3}{9}=\frac{81}{243}\)                     \(\frac{9}{27}=\frac{81}{243}\)                             \(\frac{3}{27}=\frac{9}{81}\)

\(\frac{3}{81}=\frac{9}{243}\)                      \(\frac{9}{81}=\frac{27}{243}\)                           \(\frac{3}{9}=\frac{27}{81}\)

\(\frac{9}{3}=\frac{243}{81}\)                       \(\frac{27}{9}=\frac{243}{81}\)                           \(\frac{9}{3}=\frac{81}{27}\)

 \(\frac{243}{9}=\frac{81}{3}\)                    \(\frac{81}{9}=\frac{243}{27}\)                           \(\frac{81}{9}=\frac{27}{3}\)

Khó quá 

a: Được

b: Không

c: Được