Hi

I have this calculus question question which has caused me some trouble:

$\displaystyle z = y + f(x^2 - y^2) $

Where f is diffentiable

I need to show that

$\displaystyle y \frac{\partial z}{\partial x} + x \frac{\partial z}{\partial y} = x$

How do I show that?

Is it by using the chain rule ?

/Fred