网页Geometric Interpretation. We consider the quasilinear partial differential equation in two independent variables, a(x, y, u)ux + b(x, y, u)uy − c(x, y, u) = 0. Let u = u(x, y) be a solution of this equation. Then, f(x, y, u) = u(x, y) − u = 0. describes the solution surface, or …