2017-II-01

15-06-2023 app.cch 尚無留言

答案：A

\begin{array}{cl} 3 m^{2} - 5 m n + 2 n^{2} + m - n \\ = & (3 m - 2 n) (m - n) + (m - n) \\ = & (m - n) (3 m - 2 n + 1) \end{array}