中文说明：
本代码为牛顿下山法求解非线性方程组。其调用格式为[r,m]=mulDNewton(F,x0,eps) 其中F:非线性方程组，x0：初始解，eps：解的精度；r：求得的一组解，n：迭代步数。
English Description：
This code is Newton downhill method for solving nonlinear equations. The calling format is [R, M] = muldnewton (F, x0, EPS), where f: nonlinear equations, x0: initial solution, EPS: accuracy of solution; r: N: the number of iteration steps