# Chain rule

• Sep 20th 2005, 10:52 AM
Mathman24
Urgent help needed
Hi

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

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

Where f is diffentiable

I need to show that

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

How do I show that?

Is it by using the chain rule ?

/Fred
• Sep 20th 2005, 10:27 PM
rgep
Yes, use the chain rule. For example, partial d/dx of f(x^2-y^2) is f'(x^2-y^2) times partial d/dx of (x^2 - y^2). Here f' denotes the derivative of f as a function of a single variable.