Consider the following premises. forall x_1: T_2(x_1) -> P_1(x_1). exists x_1: T_2(x_1) <-> P_1(x_1). Can we infer exists x_1: T_2(x_1) <-> P_1(x_1) from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.