Limit of a recursive succession

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SUMMARY

The limit of the recursive succession defined by a1 = sqrt(b) and an+1 = sqrt(b + an) converges to a solution of the polynomial equation x^2 - x - b = 0, where b > 0. Assuming the sequence has a limit, both lim a_(n+1) and lim a_n equal x. The solutions to this polynomial provide the limits of the succession.

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Homework Statement



Find the limit of the following succession:

a1 = sqrt(b)

an+1 = sqrt(b + an)

where b>0 is a real number.


I've thought about this really hard and could´t come up with an answear.
Please help!
 
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lim a_(n+1) = lim sqrt(b+a_n) , right?

Do you agree that
lim a_n+1 = lim a_n =x ? (I assume we have already shown the sequence has a limit)

If so then,

x = sqrt(b+ x)

x^2 -x-b=0

Your limit is one of the solutions to that polynomial.
 

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