Cho tỉ lệ thức \(\dfrac{x}{{15}} = \dfrac{{ - 4}}{5}\) thì:

\(a = c\)

\(a.c = b.d\)

\(a.d = b.c\)

\(b = d\)

\(\dfrac{5}{{35}} = \dfrac{9}{{63}}\)

\(\dfrac{{63}}{9} = \dfrac{{35}}{5}\)

\(\dfrac{{35}}{9} = \dfrac{{63}}{5}\)      

\(\dfrac{{63}}{{35}} = \dfrac{9}{5}\)

\(\dfrac{7}{{12}}\) và \(\dfrac{5}{6}:\dfrac{4}{3}\)

\(\dfrac{6}{7}:\dfrac{{14}}{5}\) và \(\dfrac{7}{3}:\dfrac{2}{9}\)

\(\dfrac{{15}}{{21}}\) và \( - \dfrac{{125}}{{175}}\)

\(\dfrac{{ - 1}}{3}\)  và \(\dfrac{{ - 19}}{{57}}\)      

\(\dfrac{2}{a} = \dfrac{5}{b}\)

\(\dfrac{b}{5} = \dfrac{2}{a}\)

\(\dfrac{2}{5} = \dfrac{a}{b}\)

\(\dfrac{2}{b} = \dfrac{5}{a}\)

\(x = \dfrac{1}{5}\)

\(x =  - \dfrac{5}{4}\)

\(x = \dfrac{5}{4}\)

\(x = \dfrac{4}{5}\)

\(1\)

\(2\)

\(0\)

\(3\)