Chapter 3 Exercise 1, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

*3.1 (Algebra: solve quadratic equations) The two roots of a quadratic equation ax2 + bx + c = 0 can be obtained using the following formula:

b2 - 4ac is called the discriminant of the quadratic equation. If it is positive, the equation has two real roots. If it is zero, the equation has one root. If it is negative, the equation has no real roots. Write a program that prompts the user to enter values for a, b, and c and displays the result based on the discriminant. If the discriminant is positive, display two roots. If the discriminant is 0, display one root. Otherwise, display “The equation has no real roots”. Note that you can use Math.pow(x, 0.5) to compute 2x. Here are some sample runs.

import java.util.Scanner;
 
public class ProgrammingEx3_1 {
 
 public static void main(String[] args) {
  Scanner input = new Scanner(System.in);
 
  System.out.print("Enter a, b, c:");
  double a = input.nextDouble();
  double b = input.nextDouble();
  double c = input.nextDouble();
  double discriminant = Math.pow(b, 2) - 4 * a * c;
 
  if (discriminant < 0) {
   System.out.println("The equation has no real roots");
   System.exit(0);
  }
 
  double r1 = (-b + Math.sqrt(discriminant)) / (2 * a);
  double r2 = (-b - Math.sqrt(discriminant)) / (2 * a);
 
  if (discriminant > 0) {
   System.out.println("The equation has two roots " + r1 + " and "
     + r2);
  } else {
   System.out.println("The equation has one root " + r1);
  }
 
 }
}