function [x_star,index,it] = Newton(fun,x,ep,it_max)
it_max=1000;ep=1e-5;
index= 0; k=1;
while k <= it_max
    x1 = x; 
    f = feval(fun,x);% f(1)時，調用第一個方程；f(2)時，調用第二個方程
    if abs(f(2))< ep break; end
    x = x - f(1)/f(2);
    if abs (x-x1) < ep index=1; break ; end
    k= k + 1;
end
x_star = x; it = k;