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问题 解答题

已知等差数列{an}中，Sn是它前n项和，设a6=2，S10=10．

（1）求数列{an}的通项公式；

（2）若从数列{an}中依次取出第2项，第4项，第8项，…，第2n项，…，按取出的顺序组成一个新数列{bn}，试求数列{bn}的前n项和Tn．

答案

（1）设数列{an}首项，公差分别为a1，d．

则由已知得a1+5d=2①

10a1+

10×9
2
d=10②

联立①②解得a1=-8，d=2，

所以an=2n-10（n∈N*）．

（2）bn=a2n=2•2n-10=2n+1-10（n∈N*），

所以Tn=b1+b2+…+bn=

4(1-2n)
1-2
-10n=2n+2-10n-4．

单项选择题

骨折的治疗原则是

A．抢救生命、保护患肢

B．徐速转送、积极治疗

C．复位、固定、功能锻炼

D．保证不出现畸形愈合

E．消除疼痛改善功能
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单项选择题

VRML is a (71) for 3D multimedia and shared virtual worlds on the WWW. In comparison to HTML, VRML adds the next level of interaction, structured graphics, and extra (72) (z and time) to the presentation of documents. The applications of VRML are (73) , ranging from simple business graphics to entertaining WWW page graphics, manufacturing, scientific, entertainment, and educational applications, and 3D shared virtual worlds and communities.
X3D is the name under which the development of VRML is continued. X3D is based on XML and is backwards (74) with VRML. Furthermore, it is componentized, profiled, and extensible, which makes it possible to use X3D in very different (75) , from high-end visualizations to lightweight applications.

A．broad

B．implicit

C．explicit

D．special
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