[tex]\overline{1a7b} ~ \vdots ~ 45 \Rightarrow \overline{1a7b} ~ \vdots ~5 ~si~ \overline{1a7b} ~ \vdots ~9~ \\ (pentru~ca~45=5 \cdot 9,~iar~5~si~9~sunt~prime~intre~ele.). \\ \\ \overline{1a7b} ~ \vdots ~ 5 \Rightarrow b \in \{0;5\}. \\ \\ \overline{1a7b}~ \vdots ~9 \Rightarrow 1+a+7+b=8+a+b ~ \vdots ~ 9. \\ \\ 1.~b=0 \Rightarrow 8+a ~ \vdots ~ 9 \Rightarrow a =1. \\ 2.~b=5 \Rightarrow 13+a ~ \vdots ~9 \Rightarrow a=5.
\\ \\ Numerele~sunt~1170~si~1575.[/tex]
