Hi!

I have this funtion: and if

so if I want to demonstrate it is differentiable in , here is what I do:

1) I check if is continuous in .

2) I find partial derivatives.

3) I check if partial derivatives are continuous in (0,0).

In case steps 1) and 3) are affirmatives, the function is differentiable in .

Too wrong?

So, in this case:

1)It is continuous.

2) I calculate partial derivate respect x:

When I calculate the limit of partial derivate respect in (0,0) and it doesn't exit, so partial derivates are not continuos in so is not differentiable,

Right?

Thank you very much! Great forum!