40. 解：原式＝2+1－9+1 ································································································ 4分

　　　　　　 ＝－5　······································································································ 6分

39. 解：

38.

解：原式=

37.

解：原式

36. 解：原式=-2+1………………………………………………6分

　　　　　　　 =3-(2-)+1……………………………………………7分

　　　　　　　 =2+………………………………………………………8分

35.　　　　

解：=·············································································· 4分

　　　　 =0 ·················································································································· 6分

34. 解：原式

33.　 解：原式＝5+1-＝5

32. 解：原式= 2－+－1　 =1.

31. 解:　原式＝　　　　　　　　

　　　　 　＝　 　　　　　　　　　　　　

　　　　 　　＝1　　　　　　 　　　　　　　　　　　　　

　　 (注：只写后两步也给满分.)