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
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