By considering different paths of approach show that the function f(x,y)=(x^2y)/(x^4+y^2) has no limit as (x,y) (0,0)

Respuesta :

Consider a path traced by an arbitrary power function [tex]y=x^n[/tex], where [tex]n\in\mathbb Z[/tex]. Then

[tex]\displaystyle\lim_{(x,y)\to(0,0)}\frac{x^2y}{x^4+y^2}=\lim_{x\to0}\frac{x^{n+2}}{x^4+x^{2n}}=\lim_{x\to0}\frac{x^{n-2}}{1+x^{2(n-2)}}[/tex]

When [tex]n=2[/tex], we have

[tex]\displaystyle\lim_{x\to0}\frac1{1+1}=\frac12[/tex]

but for any larger [tex]n[/tex], say [tex]n=3[/tex], we have

[tex]\displaystyle\lim_{x\to0}\frac x{1+x^2}=0[/tex]

Therefore the limit does not exist/is path-dependent.