Consider the following premises. ~u. p_9 or ~u. p_9 <-> u. Can we infer ~p_9 from them?
 From p_9 or ~u we can infer u -> p_9. From p_9 <-> u we can infer p_9 -> u. From p_9 -> u, u -> p_9 we can infer p_9 <-> u. Finally, from p_9 <-> u, ~u we can infer ~p_9. Therefore, the answer is yes.