4.2

package proj1;

import java.util.Scanner;


public class P42
{
	private static final double eps = (double) 1E-15 ;
	public static void main(String[] args)
		{
			Scanner in = new Scanner(System.in);
			System.out.println ("a = ");
			double a = in.nextInt();
			System.out.println ("b = ");
			double b = in.nextInt();
			System.out.println ("c = ");
			double c = in.nextInt();
			System.out.println ("x0 = ");
			double x = in.nextInt();
			double y = x - (a*x*x+b*x+c)/(2*a*x+b) ;
			int k = 1;
			while (y - x < eps )
				{
					x = y ;
					y = x - (a*x*x+b*x+c)/(2*a*x+b) ;
					k ++;
				}
			System.out.println ( "Xn = " + x +'\n' + "Xn+1 = " + y);
		}

}