Explicație pas cu pas:
[tex]\frac{\overline {1x}}{\overline {x1}}, \ x \not= 0 \\ [/tex]
[tex]\frac{\overline {1x}}{\overline {x1}}\in \Big\{ \frac{11}{11} ; \frac{12}{21} ;\frac{13}{31};\frac{14}{41};\frac{15}{51};\frac{16}{61};\frac{17}{71};\frac{18}{81};\frac{19}{91}\Big\} \\ [/tex]
