To prove the property (AB)+=(B+)(A+), one must start by invoking the definitions of adjoint operators and the inner product. The adjoint of an operator A, denoted A+, satisfies the relation ⟨Ax, y⟩ = ⟨x, A+y⟩ for all vectors x and y. By applying this definition to the product of two operators AB, the proof involves manipulating the inner products and using the linearity of the operators. The discussion emphasizes the importance of understanding the underlying definitions and properties of adjoint operators to establish the proof correctly. Mastery of these concepts is crucial for further exploration in quantum mechanics.