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× Java Examples


A standard form of a quadratic equation is:

ax2 + bx + c = 0

Where:

a, b and c are real numbers and a ≠ 0.

Roots of the equation are:

Roots of quadratic equation

For Example:

The roots of equation x2 + 5x + 4 = 0 is

Roots of quadratic equation

The roots of the equation will be imaginary if D = b2 - 4ac < 0. For example - the roots of equation x2 + 4x + 5 = 0 will be

Roots of quadratic equation

Example: Calculate roots of a Quadratic equation

In the below example, a method called roots is created which takes a, b and c as arguments to calculate the roots of the equation ax2 + bx + c = 0.

import java.lang.Math;

public class MyClass {
  static void roots(double a, double b, double c) {
    double D = b*b - 4*a*c;
    if (D >= 0){
      double x1 = (-b + Math.sqrt(D))/(2*a);
      double x2 = (-b - Math.sqrt(D))/(2*a);
      System.out.println("Roots are: "+ x1 + ", " + x2);   
    } else {
      double x1 = -b/(2*a);
      double x2 = Math.sqrt(-D)/(2*a);
      System.out.println("Roots are: "+ x1 + "±" + x2 + "i"); 
    }
  }

  public static void main(String[] args) {
    System.out.println("Equation is x*x+5x+4=0"); 
    roots(1,5,4);
    System.out.println("\nEquation is x*x+4x+5=0"); 
    roots(1,4,5);
  }
}

The above code will give the following output:

Equation is x*x+5x+4=0
Roots are: -1.0, -4.0

Equation is x*x+4x+5=0
Roots are: -2.0±1.0i