2x+2yy'+2zz'=02-3y'+5z'=0得y'=(2+5z')/3代入上面x+y(2+5z')/3+zz'=0,dz/dx=z'=-(3x+2y)/(5y+3z)dy/dx=y'=(2+5z')/3=(2z-5x)/(5y+3z)
