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问题 填空题

已知数列{an}的前n项和Sn=2n2-3，则an=______．

答案

当n=1时，S1=2×12-3=-1，

当n≥2时，an=Sn-Sn-1=2n2-3-2（n-1）2+3=4n-2，

又n=1时不满足通项公式，

∴其通项公式为an=

-1，   n=1
4n-2，    n≥2
，

故答案为：an=

-1，   n=1
4n-2，    n≥2
．

完形填空

Florence Nightingale was 小题1:b_____ on 12th May, 1820. In 1851 she trained 小题2:a_____ a nurse. Two years 小题3:l_____ she went to a British military hospital so that she 小题4:c_____ help British soldiers. Before she arrived, many soldiers died in the hospital because it was dirty. Nightingale worked 小题5:.h_____ to make the hospital 小题6:c_____ and stop soldiers 小题7:d_____. When she returned to England in 1856, she was a national heroine. Nightingale wrote two books about nursing and she 小题8:a_____ started a school to 小题9:t_____ nurses. She 小题10:d_____ in London on 13th August, 1910, when she was 90 years old.
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单项选择题

担子菌亚门的主要特征是（）。

A.菌丝无隔，有性生殖产生担孢子；

B.菌丝有隔，有性生殖产生担孢子

C.菌丝无隔，有性生殖产生节孢子；

D.菌丝有隔，有性生殖产生子囊孢子
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