题目
微分方程 P(x, y)dx + Q(x, y)dy = 0 在 G 内为全微分方程的充要条件是(）在区域 G 内恒成立.A. (partial P)/(partial y) = (partial Q)/(partial y).B. (partial P)/(partial x) = (partial Q)/(partial y).C. (partial P)/(partial y) = (partial Q)/(partial x).D. P = Q.
微分方程 $P(x, y)dx + Q(x, y)dy = 0$ 在 $G$ 内为全微分方程的充要条件是(）在区域 $G$ 内恒成立.
A. $\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial y}$.
B. $\frac{\partial P}{\partial x} = \frac{\partial Q}{\partial y}$.
C. $\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial x}$.
D. $P = Q$.
题目解答
答案
A. $\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial y}$.