先对y求z/y=x((1+xy)^y)log(e)(1+xy)再对x求z/x=(y^2)(1+xy)^(y-1)
lnz=yln(1 + xy )z=e^{yln(1 + xy )}dz/dy=e^[yln(1 + xy )]{ln(1+xy)+xy/(1+xy)}dz/dx=e^[yln(1 + xy )]{y^2/(1+xy)}
Zx=y²(1+xy)^(y-1)Zy=[(1+xy)^y]*ln(1+xy)*x