用牛顿下山法求解方程：下山因子在计算过程中可以变动，一般选择下山因子时从1开始，逐次将减半进行试算，直到能使下降条件成立为止。若当计算到某步时取不到满足要求的值（或值小到无法容忍），这时称“下山失败”，需要另取初值重新算起。-Descent method with Newton' s equation: down factor in the calculation process can change, usually selected from the 1 start down factor, will be halved for successive spreadsheet until the can down the conditions established. If when calculating the time to take a step not meet the requirements of the value (or values ??too small to tolerate), then the " down failed" , you need an alternative initial re-counting.