Question Number 4596 by Yozzii last updated on 10/Feb/16
$${Use}\:{the}\:{definition}\:{of}\:{the}\:{limit}\:{of}\:{a}\:{function} \\ $$$${to}\:{prove}\:{that}\:\underset{\left({x},{y}\right)\rightarrow\left(\mathrm{0},\mathrm{0}\right)} {\mathrm{lim}}\frac{{x}^{\mathrm{4}} +{y}^{\mathrm{4}} }{{x}^{\mathrm{2}} +{y}^{\mathrm{2}} }=\mathrm{0}. \\ $$