If $(x,y)\neq (0,0)$, let $f(x,y)=(x^2-y^2)/(x^2+y^2)$. Find the limit of f(x,y) as $(x,y) \leftrightarrow (0,0)$ along the line y=mx.
By replacing y=mx, I found $f(x,y)=(1-m^2)/(1+m^2)$
Is it possible to define f(0,0) so as to make f continuous at (0,0)
This I didn't know