利用复合函数求导法则.1、 dy^2/dx^2=dy^2/dx*dx/dx^2=dy^2/dx*1/(dx^2/dx)=2x*(1/2x)=12、dy/d(1/(1-x))=dy/dx*dx/d(1/(1-x))= (2x+1)*(1/d(1/(1-x))/dx)=(2x+1)*(1/(1-x)^2)=(2x+1)(1-x)^2
