Question $1.$

Consider the function $f(x,y)=\frac{x^2{y}^3}{x^2+y^4}.$ Which of the following is the domain of this function?

$1.D_f=\{(x,y)in{R}^2|x0\}$

$2.D_f=\{(x,y)in{R}^2|y0\}$

$3.D_f=\frac{R^2}{\frac{?}{?}}\{(0,0)\}=\{(x,y)in{R}^2|x0ory0\}$

$4.D_f=R$

$5.D_f=R^2$

$6.D_f=R^3$

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ans $=$ some number $>$

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