x≤1,xÎR}.12;6.{(2,2),(2,4),(2,6),(3,3),(3,6),(4,4),(5,5),(6,6)}.$x(ØP(x)∨Q(x)).21.(R(a)∧R(b))→(S(a)∨S(b)).{(1,3),(2,2)};{(1,1),(1,2),(1,3)}.二、选择题C.2.D.3.B.4.B.D.6.C.7.C.8.A.9.D.10.B.11.B.13.A.14.A. 15.D三、计算证明题1.(1)(2)B无上界,也无最小上界。下界1,3;最大下界是3.(3)A无最大元,最小元是1,极大元8,12,90+;极小元是1.2.R={(1,1),(2,1),(2,2),(3,1),(3,2),(3,3),(4,1),(4,2),(4,3),(4,4)}.(1)(2)3.(1)s•t=s(t(x))=t(x)+3=2x+3=2x+3.(2)s•s=s(s(x))=s(x)+3=(x+3)+3=x+6,(3)s•j=s(j(x))=j(x)+3=x/4+3,(4)j•t=j(t(x))=t(x)/4=2x/4=x/2,(5)s•j•t=s•(j•t)=j•t+3=2x/4+3=x/2+3.4.(1)P(a,f(a))∧P(b,f(b))=P(3,f(3))∧P(2,f(2)) =P(3,2)∧P(2,3) =1∧0 =0.(2)"x$yP(y,x)="x(P(2,x)∨P(3,x)) =(P(2,2)∨P(3,2))∧(P(2,3)∨P(3,3)) =(0∨1)∧(0∨1) =1∧1 =1.5.(1)(2)无最大元,最小元1,极大元8,12;极小元是1.(3)B无上界,无最小上界。下界1,2;最大下界2.6.G=Ø(P→Q)∨(Q∧(ØP→R))?=Ø(ØP∨Q)∨(Q∧(P∨R))?=(P∧ØQ)∨(Q∧(P∨R))?=(P∧ØQ)∨(Q∧P)∨(Q∧R)