Formula_4471

\[D u(x) \equiv \sum_{i, j=1}^{n} A_{i j}(x) \frac{\partial^{2} u}{\partial x_{i} \partial x_{j}}+\sum_{i=1}^{n} B_{i}(x) \frac{\partial u}{\partial x_{i}}+C(x) u-F(x),\]