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问题 填空题
在等差数列{an}中，若a9=6，则a7-
1
3
a3=______．
答案

∵a9=a1+8d=6，

a7-

1
3
a3=a1+6d-
1
3
（a1+2d）=
2
3
a1+
16
3
d=
2
3
（a1+8d）=
2
3
×6=4

故答案为：4

单项选择题



What does the speaker mean a. He learned a lot of experience from observing the street life. b. He learned how to take precautions against the criminals. c. He learned to be smart by the life in New York. d. He was confident as he walked through Times Square to his office every day.
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单项选择题 B型题

性微温，能降气祛痰的药是（）

A.芥子

B.桔梗

C.前胡

D.白前

E.竹茹
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