Consider the following premises. forall x_9: P_4(x_9) <-> Q_9(x_9). forall x_9: ~P_9(x_9). forall x_9: P_9(x_9). Can we infer exists x_9: ~P_4(x_9) from them? If possible, name the inference rules being used at each step.
The premises are contradictory and we can infer anything from them. Therefore, the answer is yes.