I have f(x,y) = 2xy^2 / (x^2+y^4) if (x,y) != (0,0) and 0 if (x,y) = (0,0).

I figured I could just find that the limit as 2xy^2 / (x^2+y^4) does not equal to 0, which should show discontinuity, but it does and I don't know how else one can show discontinuity. I showed it was not differentiable with the definition of the derivative if that helps at all, but I can't reuse that. Thanks for any help.