The following partial differential equation
\(x^2 \frac{\partial^2 u}{\partial x^2}-2 x y \frac{\partial^2 u}{\partial x \partial y}\) - \(3 y^2 \frac{\partial^2 u}{\partial y^2}+\frac{\partial u}{\partial x}-\frac{\partial u}{\partial y}=0\)
is
1
elliptic in {(x, y) ∈ ℝ2 : y > 0}
2
parabolic in {(x, y) ∈ ℝ2 : x > 0, y > 0}
3
hyperbolic in {(x, y) ∈ ℝ2 : xy ≠ 0}
4
parabolic in {(x, y) ∈ ℝ2 : xy ≠ 0}