clc
clear all
close all
format compact

fi=[1 1/2 1/3 1/4;
    1/2 1/3 1/4 1/5;
    1/3 1/4 1/5 1/6;
    1/4 1/5 1/6 1/7];
F=[2/3; 2/5; 2/7; 2/9];
A=fi\F;


figure(1)
x=0:0.01:1;
P=A(1)+A(2)*x+A(3)*x.^2+A(4)*x.^3;
plot(x,P,'r+')
hold on
R=sqrt(x);
plot(x,R,'-')
hold on

E=zeros(1,101)
for i = 1:101
    E(i) = (P(i)- R(i))^2;
end

% E=(P-R).^2; wyzszy level



indexmin = find(min(E) == E);
xmin = x(indexmin);
Emin = E(indexmin);

figure (2)
plot(x,E,'g')
hold on
plot(xmin,Emin,'r*')