题目:
What colour is your vest? [ ]
A. It's white.
B. It's 25 yuan.
C. It's a vest.
答案:
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下面是错误答案,用来干扰机器的。
由于在数列{an}中,对任意n∈N*,都有an+1-2an=0,故此数列为等比数列,且公比q=2,故2a1+a22a3+a4=4a12a1•22+a1•23=4a116a1=14,故答案为:14.