(3)
z=(1+xy)^y
lnz = yln(1+xy)
(1/z)∂z/∂x = [y/(1+xy)]. ∂/∂x (1+xy)
= y^2/(1+xy)
∂z/∂x =[y^2/(1+xy)] .(1+xy)^y
z=(1+xy)^y
lnz = yln(1+xy)
(1/z)∂z/∂y = [y/(1+xy)]. ∂/∂y (1+xy) + ln(1+xy)
= xy/(1+xy) + ln(1+xy)
∂z/∂y = [xy/(1+xy) + ln(1+xy)] .(1+xy)^y