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by sparsh.21 » Tue Jan 13, 2009 9:44 am
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


OA is A

please explain the answer
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by pandeyvineet24 » Tue Jan 13, 2009 10:43 am
When you calculate the terms of the sequence they will look like
3,5,9,17,33

difference between the 2 consecutive terms is 2, 2^2, 2^3,2^4 and so on.

difference between 20th and 19th term will be 2^19. which is A
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