Question

Aflati cifrele x si y pentru care x,y+y,x aprtin numerelor naturale. (x,y+y,x numerele sunt cu linie sus)

Answer 1

[tex]\overline{x,y}+\overline{y,x}=\dfrac{\overline{xy}}{10}+\dfrac{\overline{yx}}{10}=\dfrac{\overline{xy}+\overline{yx}}{10}=\dfrac{10x+y+10y+x}{10}=\dfrac{11(x+y)}{10}\\ \in \mathbb{N}\Leftrightarrow x+y\in M_{10}\\ Dar\ cum: x+y\ \textless \ 20\Rightarrow x+y=10\\ S:(x,y)\in \{(1,9);(2,8);(3,7);_{\dots};(9,1)\}[/tex]