y'=e^f（x^2)*f'(x^2)*(x^2)'
=2xe^f（x^2)*f'(x^2)
y''=2e^f（x^2)*f'(x^2)+4x^2e^f（x^2)*[f'(x^2)]^2+4x^2e^f（x^2)*f''(x^2)求二阶导数的时候是把一阶看成三部分求导吗对的