30. 解：原式·················································································· 4分

········································································································· 5分

　　 6分

29. 解：．

·················································································································· 4分

．　 6分

28. 解：-2

27. 解：原式= + + 1

= 2

26.

25. 解：(1)原式=

24. 原式=== 0．

23.0

22. 解：原式＝－9+8－+1+　

＝

21.

解：　 原式=3+2×-1

=3+1-1

=3