Formula_25483

\[\begin{gathered}L_{u}=\sum_{i, j=1}^{n} a_{i j}(x) \frac{\partial^{2} u(x)}{\partial x_{i} \partial x_{j}}+ \\+\sum_{i=1}^{n} b_{i}(x) \frac{\partial u(x)}{\partial x_{i}}+c(x) u(x)=f(x),\end{gathered}\]