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 mini