I can't find the solution to this problem:
is says z=f(x,y) with x= 2s +3t and y=3s-2t. i have to find zss and zst.
Do i have to use chain rule or something else?
thanks
First, this is not a problem in differential equations and really belongs in the "Calculus" section. In any case, yes, you use the chain rule:
$\displaystyle \frac{\partial z}{\partial s}= \frac{\partial z}{\partial x}\frac{\partial x}{\partial s}+ \frac{\partial z}{\partial y}\frac{\partial y}{\partial s}$.
Then, of course, to get the second derivatives, do it again.