|
3. Определите тип уравнений, если u = f (t, x, y):
| \(\displaystyle 3\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} + 8\frac{\partial^2 u}{\partial t^2} - \frac{\partial u}{\partial x} + 11\frac{\partial u}{\partial t} = 7u + 5t\) |
|
| \(\displaystyle 3\frac{\partial^2 u}{\partial x^2} - \frac{\partial^2 u}{\partial t^2} = 4\frac{\partial u}{\partial x} + 7\frac{\partial u}{\partial y}\) |
|
| \(\displaystyle \frac{\partial u}{\partial t} = 2\frac{\partial^2 u}{\partial x^2} + 10\frac{\partial^2 u}{\partial y^2} + e^{3xy}\) |
|
|