Tuesday, July 2, 2019

radicals - Prove that the limit of $sqrt{n+1}-sqrt{n}$ is zero



How would I go about proving that $\lim_{n\to\infty}\sqrt{n+1}-\sqrt{n}=0$? I have tried to use Squeeze theorem but have not been able to come up with bounds that converge to zero. Additionally, I don't think that converting to polar is possible here.



Answer



$$ \sqrt{n+1}-\sqrt{n}
= \frac{(\sqrt{n+1}-\sqrt{n})(\sqrt{n+1}+\sqrt{n})}{\sqrt{n+1}+\sqrt{n}}
= \frac{1}{\sqrt{n+1}+\sqrt{n}}
< \frac{1}{2\sqrt{n}}
$$


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