Premise: P∞Q→R∨S, R∨S→W, conclusion: p → w.
(1)P P (additional service address)
(2)P∞Q T
(3)P∨Q→R∨S P
(4)R∞S T(2)(3)
(5)R∞S→W P
(6) Watt (4)(5)
(7)P→W CP
5.(2) There is no maximal element, no minimal element, 2,5 is maximal element, 1, 3 is minimal element, and there is no upper bound, lower bound and lower bound.
6. according to the topic, there are u 1, v 1 a*u 1=v 1*a=a, u, v has a*u=v*a=x, so X * U 1 =