please help me solve this thermodynamics problem

Let M be a molar thermodynamic property as a function of T,P and x. Alternatively, let any thermodynamic properties be expressed in implicit form as nM=f(T,P,n1,n2,n3,,nm,), where n=ini and ni= the number of moles of species i . Please derive the complete Gibbs-Duhem equation of for M. What is the significance of the Gibbs-Duhem Equation