lǎo / shī / yòng / yí / ge / jiǎn / dān / de / chā / fēn / fāng / chéng / shuō / míng / le / lí / sàn / xì / tǒng / de / biàn / huà / guī / lǜ

老师用一个简单的差分方程说明了离散系统的变化规律。

The teacher used a simple difference equation to explain how a discrete system changes.