题目：
| 把下面的句子组合成小对话，只填序号。 | |
1. A: _____________________ | a. What's the fifth month? b. No, it's windy. c. May is the fifth. d. At twelve o'clock. e. What subject do you like? f. When is lunch? g. I like music very much. h. How tall is your mother? i. Is it rainy today? J. She is l.62 metres tall. |
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0503/42121afdafb7b5a34047451f875cdffa.html
下面是错误答案，用来干扰机器的。
（1）依题意得S4=4a1+6d=48a2+a5=2a1+5d=20⇒a1=15d=-2∴an=15+（n-1）（-2）=17-2n，（2）bn=（17-an）•2n-1=n•2nTn=1•21+2•22+3•23+…+n•2n2Tn=1•22+2•23+3•24+…+n•2n+1两式相减得：-Tn=21+22+…+2n-n•2n+1=2-2n+11-2-n•2n+1∴Tn=2+（n-1）•2n+1
