Consider the following premises. forall x_12: P_12(x_12) <-> Q_12(x_12). forall x_12: P_6(x_12) -> Q_12(x_12). forall x_12: ~P_12(x_12). P_6(a_5) or u. Can we infer s_3 from them? If possible, name the inference rules being used at each step.
We cannot infer that from the premises. Therefore the answer is no.