Proving convergence of Sequence dependent on previous terms

tallandpoofy
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Homework Statement



Let x1 > 9000, and

xn+1 = )2009xn + 2010)/2011 for n >1

show that (xn) converges and find its limit


Homework Equations



Definition of a limit, Monotone Convergence Theorem.

The Attempt at a Solution



Since xn+1 is monotone for n>1 and bounded, then it converges by Monotone Convergence Theorem.

How do i prove monotone for this function?
I tried xn+2 - xn+1 < 0 but it does not work since xn+1 is dependent on xn
 
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tallandpoofy said:

Homework Statement



Let x1 > 9000, and

xn+1 = )2009xn + 2010)/2011 for n >1

show that (xn) converges and find its limit


Homework Equations



Definition of a limit, Monotone Convergence Theorem.

The Attempt at a Solution



Since xn+1 is monotone for n>1 and bounded, then it converges by Monotone Convergence Theorem.

How do i prove monotone for this function?
I tried xn+2 - xn+1 < 0 but it does not work since xn+1 is dependent on xn

You should be able to use your approach to prove monotonicity. Compute nth term minus (n+1)th term in terms of nth term (equivalent to your suggestion). Then analyze under what conditions it is positive (meaning sequence is monotonically decreasing). This analysis should also give you a clue about the limit.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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