Quadtratics solver Java

import java.util.Scanner;


public class EquationsMain {

    /**
     * @param args
     */
    public static void main(String[] args)
    {
        double a, b, c, vx, vy, xans1, xans2;
        Scanner i = new Scanner(System.in);
        boolean doAgain;
        do
        {
            doAgain=false;
            System.out.print("A value: ");
            a = i.nextDouble();
            i.nextLine();
            System.out.print("B value: ");
            b = i.nextDouble();
            i.nextLine();
            System.out.print("C value: ");
            c = i.nextDouble();
            i.nextLine();
            String e = "Equation: " + a + "x^2";
            if(b<0)
            {
                e += "" + b + "x";
            }
            else if(b>0)
            {
                e += "+" + b + "x";
            }
            if(c<0)
            {
                e += "" + c;
            }
            else if(c>0)
            {
                e += "+" + c;
            }
            e += "=0";
            System.out.println(e);
            String s = "Solution: ";
            xans1 = ((b*-1) + Math.sqrt((b*b)-4*a*c))/(2*a);
            xans2 = ((b*-1) - Math.sqrt((b*b)-4*a*c))/(2*a);
            vx=-(b)/(2*a);
            vy = a*(vx*vx) + b*vx + c;
            double b2 = b*b, a2 = a* -4;
            double discr = b2 + (a2*c);
            s+= xans1;
            if(xans1 != xans2)
            {
                s+= ", ";
                s+= xans2;
            }
            if(((b*b)-4*a*c) < 0)
            {
                System.out.println("There are no solutions.");
            }
            else
            {
                System.out.println(s + '\n' + "Time: " + (Math.sqrt(xans2)));
            }
            System.out.println("Exact answer: (" + -b + " +/- Sqrt(" + discr + ")) / " + (a*2));
            String v = "Vertex: (" + vx + ", " + vy + ")";
            System.out.println(v + "\nDiscriminant: " + discr);

            double x2=vx+1, x3=vx+2, y2, y3;
            y2 = a*(x2*x2) + b*x2 + c;
            y3 = a*(x3*x3) + b*x3 + c;

            System.out.println("  x  |  y  ");
            System.out.println("-----------");
            System.out.println( x2+" | "+y2 );
            System.out.println( x3+" | "+y3 );

            boolean v1;
            do
            {
                System.out.print("Do another equation? ");
                String d = i.nextLine();
                String yn = d.charAt(0) + "";
                v1=true;
                if(yn.equalsIgnoreCase("y"))
                {
                    doAgain=true;
                }
                else if(!(yn.equalsIgnoreCase("n")))
                {
                    System.out.println("Please type YES or NO");
                    v1=false;
                }
            }
            while(!v1);
        }
        while(doAgain);
    }
}