function x = newton(f, g, x_0, tol, tol_0)
	if (tol > 0.0001 * tol_0)
		drawtol = tol;
	else
		drawtol = 0.0001 * tol_0;
	end
	x_plot = x_0-tol_0:drawtol:x_0+tol_0;
	plot(x_plot, f(x_plot));
	hold on;
%	plot([x_0-tol_0, x_0+tol_0], [x_0-tol_0, x_0+tol_0]);
%	plot(x_plot, f(x_plot));
	if (g(x_0) ~= 0)
		x = fpi_err(@(x) x-f(x)./g(x), x_0, tol, tol_0);
	else
		x = fpi_err(@(x) x-f(x)./(f(x+0.5)-f(x-0.5)), x_0, tol, tol_0);
	end