Find $\frac{\partial z}{\partial x}$ and $\frac{\partial z}{\partial y} $ if
$z=pq+qw$
$p=2x-y$, $q=x-2y$ and $w=-2x-2y$
Is $\frac{\partial z}{\partial x}$ equals to:
$\frac{\partial z}{\partial p} \frac{\partial p}{\partial x}+ \frac{\partial z}{\partial q} \frac{\partial q}{\partial x}+ \frac{\partial z}{\partial q} \frac{\partial q}{\partial x}+ \frac{\partial z}{\partial w} \frac{\partial w}{\partial x}$
Or $\frac{\partial z}{\partial p} \frac{\partial p}{\partial x}+ \frac{\partial z}{\partial q} \frac{\partial q}{\partial x}+ \frac{\partial z}{\partial w} \frac{\partial w}{\partial x}$
I can complete the solution, I need only the correct rule. Thanks
$\frac{\partial z}{\partial x}=\frac{\partial z}{\partial p} \frac{\partial p}{\partial x}+ \frac{\partial z}{\partial q} \frac{\partial q}{\partial x}+ \frac{\partial z}{\partial w} \frac{\partial w}{\partial x}=$, then
$\frac{\partial z}{\partial x}=p+w$ and
$\frac{\partial z}{\partial y}=-3q-2p-2w$