最速下降法，用于解决二维情况下的函数极值问题。通过确定初始点，通过迭代将初始点加至最小点。步长和方向为迭代的元素，每次先去步长和其点的负梯度。-The steepest descent method for solving the function extremum problems in the two-dimensional case. Iteration by determining the initial point initial point was added to the minimum point. Step iteration elements, each time to go to the step and its point of negative gradient.