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In the infinite sequence a1, a2, a3, ..., an, each term after the firs [#permalink]
21 Apr 2010, 05:49

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Difficulty:

25% (medium)

Question Stats:

86% (01:57) correct
14% (01:56) wrong based on 49 sessions

In the infinite sequence a_1, a_2, a_3,...., a_n, each term after the first is equal to twice the previous term. If a_5-a_2=12, what is the value of a_1?

Re: In the infinite sequence a1, a2, a3, ..., an, each term after the firs [#permalink]
21 Apr 2010, 06:37

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In the infinite sequence a_1, a_2, a_3,...., a_n, each term after the first is equal to twice the previous term. If a_5-a_2=12, what is the value of a_1?

A. 4 B. 24/7 C. 2 D. 12/7 E. 6/7

The formula for calculating n_{th} term would be a_n=2^{n-1}*a_1 . So: a_5=2^4*a_1; a_2=2*a_1;

Re: In the infinite sequence a1, a2, a3, ..., an, each term after the firs [#permalink]
05 Sep 2014, 11:21

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