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题库 / Prep2007E1-PS-37
For every integer k from 1 to 10, inclusive, the kth term of a certain sequence is given by ~$\left ( -1 \right )^{k+1}\left ( \frac{1}{2^{k}} \right )$~. If T is the sum of the first 10 terms in the sequence, then T is
greater than 2
between 1 and 2
between ~$\frac{1}{2}$~ and 1
between ~$\frac{1}{4}$~ and ~$\frac{1}{2}$~
less than ~$\frac{1}{4}$~
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首项是1/2，公比是-1/2，项数是10，Sn=1/3(1023/1024)=1/3,选D
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