三u=x-y,v=xy,w=x^2+y^2z'x=f'u*u'x+f'v*v'x+g'w*w'x=f'u+f'v*y+g'w*2xz'y=f'u*u'y+f'v*v'y+g'w*w'y=-f'u+f'v*x+g'w*2yz''xy=(z'x)'y=(f'u+f'v*y+g'w*2x)'y=f''u*u'y+f''v*v'y*y+f'v*y'+g''w*w'y*2x=-f''u+f''v*xy+f'v+g''w*4xy