迭代法求解非线性方程的解，包括二分法、牛顿法及抛物线法-Iterative method for solving nonlinear equations, including the dichotomy, Newton' s method and the parabolic law

用LU分解法解线性方程组Ax=b。用牛顿法求非线性方程f(x)=0-With the LU decomposition method of solving linear equations Ax = b. Using Newton s method for nonlinear equation f (x) = 0