{$N+}Program M;

CONST
     presnost=1.0e-6;

FUNCTION poly(x:real):real;
BEGIN
    poly:=4*x*x*x-2*x*x-4*x-3;
END;

VAR
   n:integer;
   x0,x1,x2,xn,xn0,y0,y1,y2,yn,a0,a1,a2,A,B,C:real;

BEGIN

n:=1;

x0:=1;
x1:=2;
x2:=1.1;

y0:=poly(x0);
y1:=poly(x1);
y2:=poly(x2);

WHILE (abs(y2)>presnost) DO
BEGIN
    WRITELN('Krok ',n,' koren ',x2:6:5,' hodnota ',y2:6:5);
    a0:=y0/((x0-x1)*(x0-x2));
    a1:=y1/((x1-x0)*(x1-x2));
    a2:=y2/((x2-x0)*(x2-x1));
    A:=a0+a1+a2;
    C:=x1*x2*a0 + x0*x2*a1 + x0*x1*a2;
    B:=-(x1+x2)*a0 -(x0+x2)*a1 -(x0+x1)*a2;

    xn:=(-B+sqrt(B*B-4*A*C))/(2*A);
    xn0:=(-B-sqrt(B*B-4*A*C))/(2*A);

    IF (abs(xn0-x2)<abs(xn-x2)) THEN xn:=xn0;

    x0:=x1;
    x1:=x2;
    x2:=xn;
    y0:=y1;
    y1:=y2;
    y2:=poly(xn);

    n:=n+1;
    READLN;
END;

WRITELN('Konec');
READLN;

END.