Let `z(x,y)= 4x^2-3y^2` where `x = 2s+5t & y = -8s-6t`.

Calculate (\partial z)/(\partial s)` & `(\partial z)/(\partial t)` by first finding (\partial

x)/(\partial s)`, `(\partial y)/(\partial s)`, `(\partial x)/(\partial t)` & `(\partial y)/(\partial t)`

and using the chain rule.