创建一个Java程序来求解二次方程

Question

Solving a quadratic equation

I have the following written down so far. I am not sure on how to introduce the second method

public static void main(string args[]){

}

public static  double quadraticEquationRoot1(int a, int b, int c) (){

}

if(Math.sqrt(Math.pow(b, 2) - 4*a*c) == 0)
{
    return -b/(2*a);
} else {
    int root1, root2;
    root1 = (-b + Math.sqrt(Math.pow(b, 2) - 4*a*c)) / (2*a);
    root2 = (-b - Math.sqrt(Math.pow(b, 2) - 4*a*c)) / (2*a);
    return Math.max(root1, root2);  
}

}

Answer 1

Firstly, your code won't compile--you have an extra } after the start of public static double quadraticEquationRoot1(int a, int b, int c) () .

Secondly, you aren't looking for the correct input types. If you want input of type double , make sure you declare the method appropriately. Also be careful of declaring things as int when they could be doubles (for example, root1 and root2 ).

Thirdly, I don't know why you have the if/else block--it would be better to simply skip it, and only use the code that is currently in the else part.

Finally, to address your original question: Simply create a separate method and use Math.min() instead of Math.max() .

So, to recap in code:

public static void main(string args[]){

}

//Note that the inputs are now declared as doubles.
public static  double quadraticEquationRoot1(double a, double b, double c) (){    
    double root1, root2; //This is now a double, too.
    root1 = (-b + Math.sqrt(Math.pow(b, 2) - 4*a*c)) / (2*a);
    root2 = (-b - Math.sqrt(Math.pow(b, 2) - 4*a*c)) / (2*a);
    return Math.max(root1, root2);  
}

public static double quadraticEquationRoot2(double a, double b, double c) (){    
    //Basically the same as the other method, but use Math.min() instead!
}

Answer 2

Well why don't you try to use the same exact algorithms but then use Math.min in your return statement?

Also, note that you're not taking into account whether or not $b$ is negative in your first if statement. In other words you simply return $-b / 2a$ but you don't check if $b$ is negative, if it isn't then this is actually the smaller of the two roots not the larger. Sorry about that! I misinterpreted what was going on xD

Answer 3

package QuadraticEquation;

import javax.swing.*;

public class QuadraticEquation {
   public static void main(String[] args) {
      String a = JOptionPane.showInputDialog(" Enter operand a :  ");
      double aa = Double.parseDouble(a);
      String b = JOptionPane.showInputDialog(" Enter operand b :  ");
      double bb = Double.parseDouble(b);
      String c = JOptionPane.showInputDialog(" Enter operand c :  ");
      double cc = Double.parseDouble(c);
      double temp = Math.sqrt(bb * bb - 4 * aa * cc);
      double r1 = ( -bb + temp) / (2*aa);
      double r2 = ( -bb -temp) / (2*aa);
      if (temp > 0) {
            JOptionPane.showMessageDialog(null, "the equation has two real roots" +"\n"+" the roots are : "+  r1+" and " +r2);

        }
      else if(temp ==0) {
            JOptionPane.showMessageDialog(null, "the equation has one root"+  "\n"+ " The root is :  " +(-bb /2 * aa));

        }

      else{

            JOptionPane.showMessageDialog(null, "the equation has no real roots !!!");
        }
    }        
}