Limit of a squareroot combination.

  • Thread starter Thread starter Dissonance in E
  • Start date Start date
  • Tags Tags
    Combination Limit
Dissonance in E
Messages
71
Reaction score
0

Homework Statement


find lim x---> infinity
sqrt(x + sqrt(x)) - sqrt(x)


Homework Equations


Conjugate multiplication.



The Attempt at a Solution


Ok so i know this is probably very easy yet it confuses me.
Im guessing youd need to multiply the numerator & denominator by the conjugate of the expression, and then work the expression into a form where all the x terms are denominators of a fraction so that as they approach inf, the fraction approaches 0.

(sqrt(x + sqrt(x)) - sqrt(x))(sqrt(x + sqrt(x)) + sqrt(x))
/ sqrt(x + sqrt(x)) + sqrt(x)

(x + sqrt(x) +sqrt(x)sqrt(x + sqrt(x)) -sqrt(x)sqrt(x + sqrt(x)) - x)
/ (sqrt(x + sqrt(x)) + sqrt(x))

sqrt(x)
/ (sqrt(x + sqrt(x)) + sqrt(x))

this is as far as i get, any help would be appreciated.

P.s: does this forum have a way of writing maths in a bit more easily comprehendable form?
 
Physics news on Phys.org
There should be a guide to using latex somewhere around here.

\sqrt{x+\sqrt{x}}=\sqrt{x} \sqrt{1+\sqrt{x}/x}

If you click on that it should pop up a window showing what I typed in. Sorry, I'm not all that good at it. By the way, that's your next step as well.
 
Last edited:
All right so we have:
sqrt(x)
/ (sqrt(x + sqrt(x)) + sqrt(x))

sqrt(x)
/ (sqrt(x) sqrt(1+sqrt(x)/x) + sqrt(x)

1 / sqrt(1+sqrt(x)/x) + 1

sqrt(x)/x tends to zero when x ---> infinity

1 / sqrt(1) +1

1/2

K that makes sense now, thank you.
And sry bout the lack of latex notation, il look into it for next time!
 
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...
Back
Top