F(x-y,y-z)=0,求δz/δx对x求导 F1'(x-y,y-z) (x-y)'+F2'(x-y,y-z) (y-z)' =0F1'(x-y,y-z) +F2'(x-y,y-z) (-δz/δx)=0δz/δx=F1'(x-y,y-z) /F2'(x-y,y-z)
