Tuesday, 5 September 2017

calculus - Find: $limlimits_{xto +infty}xleft(sqrt{x^{2}+1}-sqrt[3]{x^{3}+1}right)$

Calculate the following limit:




$$\displaystyle\lim_{x\to +\infty}x\left(\sqrt{x^{2}+1}-\sqrt[3]{x^{3}+1}\right)$$




I need find this limit without l'Hospital or Taylor series.




Wolfram alpha gives $\frac{1}{2}$



My try is:



Let: $a=\sqrt{1+x^{2}}$ and $b=\sqrt[3]{1+x^{3}}$



And we know that:



$a-b=\frac{a^{3}-b^{3}}{a^{2}+b^{2}+ab}$




But after applied this I find again the problems $0.+\infty$ indeterminate

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