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# If the sequence x1, x2, x3, , xn, is such that x1 = 3 and

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Intern
Joined: 08 Nov 2008
Posts: 38
If the sequence x1, x2, x3, , xn, is such that x1 = 3 and [#permalink]

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11 Nov 2008, 19:56
If the sequence x1, x2, x3, …, xn, … is such that x1 = 3 and xn+1 = 2xn – 1 for n ≥ 1, then x20 – x19 =

A. 2^19
B. 2^20
C. 2^21
D. 2^20 - 1
E. 2^21 - 1

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Director
Joined: 14 Aug 2007
Posts: 697

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11 Nov 2008, 20:04
gorden wrote:
If the sequence x1, x2, x3, …, xn, … is such that x1 = 3 and xn+1 = 2xn – 1 for n ≥ 1, then x20 – x19 =

A. 2^19
B. 2^20
C. 2^21
D. 2^20 - 1
E. 2^21 - 1

A

the sequence translates to Xn = 2^n + 1

X20 - x19 = 2^20 + 1 - 2^19 - 1 = 2^19(2-1) = 2^19

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This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

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Re: sequence--27   [#permalink] 11 Nov 2008, 20:04
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# If the sequence x1, x2, x3, , xn, is such that x1 = 3 and

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