Homework Help: Expansion of limit term

1. Oct 30, 2011

dannee

1. The problem statement, all variables and given/known data

i added a photo of a move of limit of function.
can anyone please explain this move ? step by step.. i can't understand it
thanks in advance !

2. Relevant equations

3. The attempt at a solution

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2. Oct 30, 2011

spamiam

Do you know what a conjugate is? Try multiplying the numerator and denominator by the conjugate of $\sqrt{x^2 + \frac{1}{n}} - x$.

3. Oct 30, 2011

thanks !!!!