# Answer to Question #48934 in Java | JSP | JSF for felly

Question #48934

Write a program to compute the roots (x1, x2) of a quadratic equation.

X=( -b ± √b²-4ac)/2a

Expert's answer

import java.util.Scanner;

public class Roots {

static double a,b,c;

static double delta;

static double x1,x2,x3;

static double Q,R,Teta;

public static void main(String[] args) {

System.out.println("Enter the coefficients for the quadratic equation");

Scanner s = new Scanner(System.in);

System.out.print("a->");

a = s.nextDouble();

System.out.print("b->");

b = s.nextDouble();

System.out.print("c->");

c = s.nextDouble();

delta = Math.pow(b,2)-4*a*c;

if (delta<0)

{

System.out.println("delta =" + delta);

System.out.println("The quadratic equation has no real roots ");

}

else

{

x1=(-b - Math.sqrt(delta))/(2*a);

x2=(-b + Math.sqrt(delta))/(2*a);

System.out.println("delta =" + delta);

System.out.println("The quadratic equation has 2 distinct real roots");

System.out.println("x1 =" + x1);

System.out.println("x2 =" + x2);

}

// TODO Auto-generated method stub

System.out.println("Enter the coefficients for the cubic equation");

Scanner cb = new Scanner(System.in);

System.out.print("a->");

a = cb.nextDouble();

System.out.print("b->");

b = cb.nextDouble();

System.out.print("c->");

c = cb.nextDouble();

delta = 4*Math.pow(a,3)*c-Math.pow(a,2)*Math.pow(b,2)+4*Math.pow(b,3)-18*a*b*c+27*Math.pow(c,2);

if (delta<0)

{

System.out.println("delta =" + delta);

System.out.println(" Then cubic equation has three distinct roots. ");

Q=(1.0/9)*(Math.pow(a, 2)-3*b);

R=(1.0/54)*(2*Math.pow(a, 3)-9*a*b+27*c);

Teta=Math.acos( R/ Math.sqrt(Math.pow(Q,3)) );

x1=-2*Math.sqrt(Q)*Math.cos(Teta/3)- (1.0/3)*a;

x2=-2*Math.sqrt(Q)*Math.cos( (Teta+2*Math.PI)/3)- (1.0/3)*a;

x3=-2*Math.sqrt(Q)*Math.cos( (Teta-2*Math.PI)/3)- (1.0/3)*a;

System.out.println("x1 =" + x1);

System.out.println("x2 =" + x2);

System.out.println("x3 =" + x3);

}

else

{

System.out.println("delta =" + delta);

System.out.println("The cubic equation has one real root and 2 complex conjugate roots");

}

}}

public class Roots {

static double a,b,c;

static double delta;

static double x1,x2,x3;

static double Q,R,Teta;

public static void main(String[] args) {

System.out.println("Enter the coefficients for the quadratic equation");

Scanner s = new Scanner(System.in);

System.out.print("a->");

a = s.nextDouble();

System.out.print("b->");

b = s.nextDouble();

System.out.print("c->");

c = s.nextDouble();

delta = Math.pow(b,2)-4*a*c;

if (delta<0)

{

System.out.println("delta =" + delta);

System.out.println("The quadratic equation has no real roots ");

}

else

{

x1=(-b - Math.sqrt(delta))/(2*a);

x2=(-b + Math.sqrt(delta))/(2*a);

System.out.println("delta =" + delta);

System.out.println("The quadratic equation has 2 distinct real roots");

System.out.println("x1 =" + x1);

System.out.println("x2 =" + x2);

}

// TODO Auto-generated method stub

System.out.println("Enter the coefficients for the cubic equation");

Scanner cb = new Scanner(System.in);

System.out.print("a->");

a = cb.nextDouble();

System.out.print("b->");

b = cb.nextDouble();

System.out.print("c->");

c = cb.nextDouble();

delta = 4*Math.pow(a,3)*c-Math.pow(a,2)*Math.pow(b,2)+4*Math.pow(b,3)-18*a*b*c+27*Math.pow(c,2);

if (delta<0)

{

System.out.println("delta =" + delta);

System.out.println(" Then cubic equation has three distinct roots. ");

Q=(1.0/9)*(Math.pow(a, 2)-3*b);

R=(1.0/54)*(2*Math.pow(a, 3)-9*a*b+27*c);

Teta=Math.acos( R/ Math.sqrt(Math.pow(Q,3)) );

x1=-2*Math.sqrt(Q)*Math.cos(Teta/3)- (1.0/3)*a;

x2=-2*Math.sqrt(Q)*Math.cos( (Teta+2*Math.PI)/3)- (1.0/3)*a;

x3=-2*Math.sqrt(Q)*Math.cos( (Teta-2*Math.PI)/3)- (1.0/3)*a;

System.out.println("x1 =" + x1);

System.out.println("x2 =" + x2);

System.out.println("x3 =" + x3);

}

else

{

System.out.println("delta =" + delta);

System.out.println("The cubic equation has one real root and 2 complex conjugate roots");

}

}}

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