说明：  牛顿迭代法以微分为基础的，微分就是用直线来代替曲线，由于曲线不规则，那么我们来研究直线代替曲线后，剩下的差值是不是高阶无穷小，使得近似得到所要求得解。
(Newton iterative method based on the differential based, differential is in a straight line to replace the curve, due to the irregular curve, we studied line instead of the curve and the rest of the difference is not higher order infinitesimal, the approximation obtained by the solution.)