[tex]\it m,\ n\in\mathbb{N};\ \ m,\ n\ <10\ \ \ \ \ (1)\\ \\ (m+n):n=n \Rightarrow m+n=n\cdot n \Rightarrow m=n\cdot n-n \Rightarrow m=n(n-1)\ \ \ \ \ (2)\\ \\ (1),\ (2) \Rightarrow \begin{cases}\it m=2,\ \ n=2\\ \\ sau\\ \\ \it m=6,\ \ n=3\end{cases}[/tex]
