微分方程，有时简称为方程，未知函数是一元函数的微分方程称作常微分方程，未知数是多元函数的微分方程称作偏微分方程。微分方程中出现的未知函数最高阶导数的阶数，称为微分方程的阶。-Differential equations, sometimes referred to as the equation, the unknown function is called Differential DOLLAR FUNCTION ordinary differential equations, differe