7. 2+2

6. 解：＝

5. 解：原式=2+1-3+2　　　　　　　　　　　　　　　　　　　　　 　……4分

　　　　　　　 =2　　　　　　　　　　　　　　　　　　　　　　　　　 ……2分

4. 解：原式························································································ 2分

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

···················································································································· 6分

3. 解：原式········································································ 4分

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

······················································································································ 6分

2. 解：原式==

1. 解：原式=2+3-1-2=2

19. 　20. 5　 　21. <　　 22. 　　23. 　　24.　 25. 47

12. 　　13. 5　 14. x≥2　 15. 3 　．　 16. ±4　 17. ；18. (或+)；

1. _2. 1　 3. 1　 4. 　5. 12　 6. 6，4　 7. 　　8. 4　 9. 　10. -1　 11.