功能：牛顿型信赖域方法求解无约束优化问题min f(x) 输入 x0是初始迭代点 输出：xk是近似极小点，val是近似极小值，k是迭代次数- function: Newton type trust region method for solving unconstrained optimization problem min f (x) input The xo is the initial iteration point output: xk is appro