public void solve(double a, double b, double c) {
        double d = discriminant(a, b, c);
        if (d < 0) {
            System.out.println("No roots");
        } else if (d > 0) {
            double x1 = (-b + Math.sqrt(d)) / (2.0 * a);
            double x2 = (-b - Math.sqrt(d)) / (2.0 * a);
            System.out.println("x1 = " + x1 + ", x2 = " + x2);
        } else {
            System.out.println("x = " + ((-b) / (2.0 * a)));
        }
    }
public void solve(double a, double b, double c)