Consider the following premises. forall x_8: ~P_8(x_8). forall x_8: P_8(x_8) <-> Q_8(x_8). u -> Q_8(a_5). Can we infer u from them?
 From forall x_8: P_8(x_8) <-> Q_8(x_8), forall x_8: ~P_8(x_8) we can infer forall x_8: ~Q_8(x_8). From forall x_8: ~Q_8(x_8) we can infer ~Q_8(a_5). Finally, from u -> Q_8(a_5), ~Q_8(a_5) we can infer ~u, which contradicts u. Therefore, the answer is no.