function [ x,fx,n ] = MetodParabole( fun,x1,x3,tol )

X = [ x1 (x1+x3)/2 x3 ]';
Y = [ [1 1 1]' X X.*X ];
F = feval(fun, X);
abc = Y \ F;
x = -abc(2) / 2 / abc(3);
fx = feval(fun,x);
n = 0;
while abs( [1 x x^2] * abc - fx ) > tol
    if (x > X(2)) && (x < X(3))
        if (fx < F(2)) && (fx < F(3))
    	 X = [X(2); x; X(3)]; F = [F(2); fx; F(3)];
        elseif (fx > F(2)) && (fx < F(3))
        X = [X(1); X(2); x]; F = [F(1); F(2); fx];
        else
            error('Greska: Fopt > min(F2,F3)')
        end %...
    % ...
    elseif (x > X(1)) && (x < X(2))
        if (fx < F(1)) && (fx < F(2))
            X = [X(1); x; X(2)]; F = [F(1); fx; F(2)];
        elseif (fx > F(2)) && (fx < F(1))
            X = [x; X(2); X(3)]; F = [fx; F(2); F(3)];
        else
            error('Greska: Fopt > min(F1,F2)')
        end
    else
        error('x lezi van granica')
    end
    Y = [ [1 1 1]' X X.*X ];
    abc = Y \ F;
    x = -abc(2) / 2 / abc(3);
    fx = feval(fun, x);
    n = n + 1;
end
end