问答题
(∀x)P(x)∧¬(∃x)Q(x),求前束范式
问答题 (x)(A(x)B(x))=>(x)A(x)(x)B(x)
问答题 (x)(A(x)→B(x))=>(x)A(x)→(x)B(x)
问答题 (x)(B→A(x))B→(x)A(x)