(1)u=f(x^2-y^2,e^(w^y))s=x^2-y^2,t=e^(w^y)u=f(s,t)u'x=f's*s'x+f't*t'x=f's*2xu'y=f's*s'y+f't*t'y=f's*(-2y)+f't*e^(w^y)*w^(y-1)*y(3)u=f(x,xy,xyz)a=x,b=xy,c=xyzu'x=f'a+f'b*y+f'c*yzu'y=f'b*x+f'c*xzu'z=f'c*xy