Determine this sequence increasing or decreasing

e179285
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A sequence (an) is recursively defined by a1 = 1 and
an+1 =1 /(2+an ) for all n≥1

I'll prove this sequence is convergent by monoton sequence theorem.ı can find ıt is bounded but ı cannot decide it is monoton because when ı write its terms,Its terms are increasing sometimes decreasing sometimes.

How can ı prove it is increasing or decreasing?
 
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e179285 said:
How can ı prove it is increasing or decreasing?

For what value of an would it be stationary, ie. an+1 = an?
 
Do an+1-an and you'll have to combine it into one fraction and then do some factoring and you'll see if it's decreasing or increasing.
 
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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