If z = f(x, y), where

Question

x = r^2 + s^2
and
y = 8rs,
find
∂^2z/(∂r ∂s).

Answer 1

∂z/∂r = ∂z/∂x ∂x/∂r + ∂z/∂y ∂y/∂r
= 2r ∂z/∂x + 8s ∂z/∂y

You haven't said what f(x,y) is, so it's a bit hard to go from here, but you know that

∂^2z/∂r∂s = ∂/ds (2r ∂z/∂x + 8s ∂z/∂y)

Answer 2

we were not given f(x,y) the whole problem is listed above, apparently there is a link that is supposed to help us but I followed it and don't know what I am doing wrong and I cannot post the link because it is on a special homework website.