A geometric approach of the generalized dʹAlembert equation

By using a geometric approach we prove that the set of solutions of the generalized dʹAlembert equation∂n log f/∂x1⋯∂xn=0,considered in domain of the (x1,…,xn)-space Rn, is larger than the set of the functions that can be represented in the form as f(x1,…,xn)=f1(x2,…,xn)⋯fn(x1,…,xn−1).