偏微分算符

贡献者： addis

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预备知识　算符

　　例如

\begin{equation} \left( \frac{\partial}{\partial{x}} + 1 \right) ^2 = \frac{\partial^{2}}{\partial{x}^{2}} + 2 \frac{\partial}{\partial{x}} + 1~, \end{equation}

\begin{equation} \left( \frac{\partial}{\partial{x}} + \frac{\partial}{\partial{y}} \right) ^2 = \frac{\partial^{2}}{\partial{x}^{2}} + \frac{\partial^{2}}{\partial{y}^{2}} + 2 \frac{\partial^2 }{\partial x \partial y} ~. \end{equation}