5. 12, 3.

6. {4}, {1, 2, 3, 4}, {1, 2}. 7. 自反性；对称性；传递性. 8. (1, 0, 0), (1, 0, 1), (1, 1, 0).

9. {(1,3),(2,2),(3,1)}; {(2,4),(3,3),(4,2)}; {(2,2),(3,3)}. 10. 2m n.

11. {x | -1≤x < 0, x R}; {x | 1 < x < 2, x R}; {x | 0≤x≤1, x R}. 12. 12; 6.

13. {(2, 2),(2, 4),(2, 6),(3, 3),(3, 6),(4, 4),(5, 5),(6, 6)}. 14. x( P(x)∨Q(x)). 15. 21.

16. (R(a)∧R(b))→(S(a)∨S(b)). 17. {(1, 3),(2, 2)}; {(1, 1),(1, 2),(1, 3)}. 二、选择题

1. C. 2. D. 3. B. 4. B. 5. 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)