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Does the following series diverge or converge? if it converges, what is the value of x?

{x=sqrt[(1 + 2*sqrt(1 + 3*sqrt(1 + 4*sqrt(1 + 5*sqrt(1 + 6))))]}......to infinity.

P.S. They are nested sqrt within sqrt within sqrt......, i.e. sqrt(1+6) is under sqrt(1+5) which is under the sqrt(1+4)...........and so on. Hint: use Wolfram/Alpha to visualize it very clearly. Thanks for help.

 Jun 11, 2016
 #1
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Thank you!. I got the answer I wanted.

 Jun 11, 2016
 #2
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x=3

 

To see why:

\(x = \sqrt(x^2)=\sqrt(x^2+1-1)\)

\(=\sqrt(1+(x-1)(x+1))=\sqrt((1+(x-1)*\sqrt((x+2)^2))\)

\(=\sqrt(1+(x-1)*(1+x(x+2))).....\)

\(3=\sqrt9=\sqrt(1+2*4)=\sqrt(1+2*\sqrt16)=\sqrt(1+2*\sqrt(1+3*5))=.....\)

 Aug 16, 2016

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