\(\eqalign{
& a)\,\,P:\,\,\,\,\forall x \in N:\,\,x|x \cr
& \,\,\,\,\,Q:\,\,\exists x \in N:\,\,x = {x^2} \cr
& Menh\,\,de\,\,P\,\,dung,\,\,Menh\,\,de\,\,Q\,\,dung\,\,\left( {0 = {0^2};1 = {1^2}} \right) \cr
& b)\,\,\overline P :\,\,\exists x \in N:\,\,x\,\,khong\,\,la\,\,uoc\,\,cua\,\,x \cr
& \,\,\,\,\,\,\overline Q :\,\,\forall x \in N:\,\,{x^2} = x \cr} \)