Persamaan kuaddrat,,,,,

public class kaka
{
public static void main(String[] args)
{
double a = 4;
double b = -13;
double c = -12;
double D = b*b - 4*a*c;
double x1, x2;
System.out.println("Persamaan kuadrat a*x^2+b*x+c=0, di mana");
System.out.println("a = " + a);
System.out.println("b = " + b);
System.out.println("c = " + c);
System.out.println("dengan menerapkan rumus ABC diketahui bahwa: ");
if(D<0)
{
System.out.println("Akar-akar persamaan imaginer.");
}
else
if(D==0)
{
System.out.println("Akar-akar persamaan nyata tetapi kembar.");
x1 = -b/(2*a);
System.out.println("x1 = x2 = " + x1);
}
else
{
System.out.println("Akar-akar persamaan nyata dan berbeda.");
x1 = (-b+Math.sqrt(D))/(2*a);
x2 = (-b-Math.sqrt(D))/(2*a);
System.out.println("x1 = " + x1 + " x2 = " + x2);
}
}
}