- 问题详情:数列{an}的前n项和为Sn,a1=1,a2=2,an+2-an=1+(-1)n(n∈N+),则S100=.【回答】由an+2-an=1+(-1)n知a2k+2-a2k=2,a2k+1-a2k-1=0,∴a1=a3=a5=…=a2n-1=1,数列{a2k}是等差数列,a2k=2k.∴S100=(a1+a3+a5+…+a99)+(a2+a4+a6+…+a100)=50+(2+4+6+…+100)=50+=2600.*:2600知识点:数列题型:填空题...
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- 问题详情:在等差数列{an}中,公差d=,前100项的和S100=45,则a1+a3+a5+…+a99=________.【回答】10知识点:数列题型:填空题...
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- 问题详情:根据句意及首字母提示完成单词。⒈ZhuangYongwonthewomen’s100-metref___________withatimeof54.64seconds.⒉Therearemanyp__________intheshoppingcenter.⒊Wemadeal____________ofrecordsforourclass.⒋Myf___________sportisplayingbasketball.⒌Whoisthec_...
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- 问题详情:一架飞机从*地(60°S,80°W)起飞,沿最近航线匀速飞行8小时抵达乙地(60°S,100°E)。据此回答5-6题。5.飞机飞行航线()A.一直不变 B.先向南后向北C.先向西北后向西南 ...
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