Functions of several variables

[Arushi :))]

F(x,y) = 2/3lnx+ 1/3 lny
i)Find dz/dt when z = F(x,y) , x = e^(3t) and y = 1+e^(-3t).
ii)Determine dz/dt as t tends to infinity .

[jack]

1) dz/dt=2e^6t-e^-3t-e^-6t
2) infinity