学习newton raphson and back eluer

 % % time step  https://ww2.mathworks.cn/matlabcentral/answers/184200-newton-raphson-loop-for-backward-euler
 % h = (t_final - t_init)/n; % with n number of time steps
 % % vectors
 % t = [tinit zeros(,n)]; % time
 % y = [yinit zeros(,n)]; % solution
 % % Backward Euler loop
 % for i = :n
 %    t(i+) = t(i) + h;
 %    y_temp = y(i) + h(f(t(i), y(i)));
 %    y(i+) = y(i) + h*f(t(i+), y_temp);
 % end
 % for i = :n
 %    error = ;
 %    tolerance = 1e-;
 %    t(i+) = t(i) + h;
 %    y_temp = y(i) + h*(f(t(i), y(i)));
 %    while error >= tolerance
 %       y(i+) = y(i) + h*f(t(i+), y_temp);
 %       error = abs(y(i+) - y_temp) % (local) absolute error
 %       y_temp = y(i+);
 %    end
 % end

 % yold = y(i)+h*f(t(i),y(i));
 % while error >= tolerance
 % ynew = yold-(yold-(y(i)+h*f(t(i+),yold)))/(-h*df(t(i+),yold));
 % error = abs(ynew-yold);
 % yold=ynew;
 % end
 % y(i+) = ynew;

 %y'=y+2*x/y^2 x=[0,2] y(0)=1  https://wenku.baidu.com/view/d18cdaa10b4c2e3f5627632f.html
 t_final=;
 t_init=;
 n=;
 tolerance=0.0000001
  h = (t_final - t_init)/n;
  ti=t_init+h;
 yold=+h*f(,);% yold = y(i)+h*f(t(i),y(i));
 while error >= tolerance
 ynew = yold-(yold-(y(i)+h*f(t(i+),yold)))/(-h*df(t(i+),yold));
 error = abs(ynew-yold);
 yold=ynew;
 end
 y(i+) = ynew;

上面代码应该怎样修改？