[tex]18\mid\bar{13y9x}\Rightarrow[/tex]
[tex]2\mid\bar{13y9x}~si[/tex]
[tex]9\mid\bar{13y9x}[/tex]
Din prima avem
[tex]x\in\{0,2,4,6,8\}[/tex]
Din a doua avem
[tex]1+3+y+9+x~\vdots~9[/tex]
[tex]4+x+y+9~\vdots~9[/tex]
[tex]4+x+y~\vdots~9[/tex]
[tex]x=0\Rightarrow4+y~\vdots~9\Rightarrow y=5[/tex]
[tex]x=2\Rightarrow6+y~\vdots~9\Rightarrow y=3[/tex]
[tex]x=4\Rightarrow8+y~\vdots~9\Rightarrow y=1[/tex]
[tex]x=6\Rightarrow10+y~\vdots~9\Rightarrow y=8[/tex]
[tex]x=8\Rightarrow12+y~\vdots~9\Rightarrow y=6[/tex]
[tex]\bar{13y9x}\in\{13590,13392,13194,13896,13698\}[/tex]
