The partial differential equation \(5\frac{{{{\rm{\partial }}^2}{\rm{z}}}}{{{\rm{\partial }}{{\rm{x}}^2}}} + 6\frac{{{{\rm{\partial }}^2}{\rm{z}}}}{{{\rm{\partial }}{{\rm{y}}^2}}} = {\rm{xy}}\) is classified as
1
elliptic
2
parabolic
3
hyperbolic
4
None of these