Simple Limits Problem: Finding the Limit of a Square Root Expression

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Homework Statement


Find
\lim_{x\rightarrow \infty} (\sqrt{x+\sqrt{x+\sqrt{x}}}-\sqrt{x})


Homework Equations





The Attempt at a Solution


Rewriting the given expression,
\sqrt{x}\left(\sqrt{1+\sqrt{\frac{1}{x}\left(1+\frac{1}{\sqrt{x}}\right)}}-1\right)
What should I do with the sqrt(x) outside? :confused:

Any help is appreciated. Thanks!
 
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A common way to approach limits of the type of ##\sqrt{x+f(x)}-\sqrt{x}## is a multiplication with ##\displaystyle 1=\frac{\sqrt{x+f(x)}+\sqrt{x}}{\sqrt{x+f(x)}+\sqrt{x}}##. This does not change the limit (as you multiply with 1), but you can simplify the numerator a lot.
 
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Pranav-Arora said:

Homework Statement


Find
\lim_{x\rightarrow \infty} (\sqrt{x+\sqrt{x+\sqrt{x}}}-\sqrt{x})

Homework Equations


The Attempt at a Solution


Rewriting the given expression,
\sqrt{x}\left(\sqrt{1+\sqrt{\frac{1}{x}\left(1+\frac{1}{\sqrt{x}}\right)}}-1\right)
What should I do with the sqrt(x) outside? :confused:

Any help is appreciated. Thanks!

I wanted to post earlier but kept messing up my algebra.

Call the expression ##y##. Find ##y.(\sqrt{x + \sqrt{x + \sqrt{x}}} + \sqrt x)##.

mfb has suggested pretty much the same thing.
 
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mfb said:
A common way to approach limits of the type of ##\sqrt{x+f(x)}-\sqrt{x}## is a multiplication with ##\displaystyle 1=\frac{\sqrt{x+f(x)}+\sqrt{x}}{\sqrt{x+f(x)}+\sqrt{x}}##. This does not change the limit (as you multiply with 1), but you can simplify the numerator a lot.

Thanks mfb! :smile:
 
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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