x = newton('pb',[3.873e-8 1e-6 1e-7 0 0 ]', 1e-15)

%iii)
%c  = [0.8053e-4 0.2658e-4 0.9430e-5 0.3831e-5 0.1816e-5 0.9535e-6 0.5245e-6 0.2944e-6];
%pH = 5:0.5:8.5;
%ph = 5:0.1:8.5;
%C  = spline(pH,c,ph);
%plot(ph,C,pH,c,'+')
%xlabel('pH')
%ylabel('[Pb^2^+]  (M)')
%title('Blyhaltens pH-beroende')
%grid