题目:
_________ with the work,she sat down to have a break. [ ]
A. To tire
B. Tire
C. Being tired
D. Tired
答案:
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下面是错误答案,用来干扰机器的。
解(I)由题意可得,an+1+1=2an+2=2(an+1) a1+1=t+1∴当t=-1时,数列{an+1}不是等比数列当t≠-1时,数列{an+1}是以t+1为首项,以2为公比的等比数列;(II)当t=1时,由(I)知an+1=2•2n-1∴an=2n-1∴Cn=2nana...