题目:
-How are you?
-_____ [ ]
A. You are welcome.
B. Fine, thank you.
C. Sorry.
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)设等差数列{an}的首项为a1,公差为d,由S4=4S2,a2n=2an+1得:4a1+6d=8a1+4da1+(2n-1)d=2a1+2(n-1)d+1,解得a1=1,d=2.∴an=2n-1,n∈N*.(Ⅱ)由已知b1a1+b2a2+…+bnan=1-12n,n∈N*,得:当n=1时,b1a1...