Thread: help!! quadratic program

What have you done so far?

i wrote the algorithm and started...

algorithm is
1. get the numbers for variables a,b and c from the given equation 0= ax^2 + bx +c.
2. declare the variables with their given numbers.
3.plug the numbers into the variables for the equation x = -b + the square root of b^2 - 4ac/2a
and solve for x.
4.plug the numbers into the variables for the equation x = -b - the square root of b^2 - 4ac/2a
and solve for x.
5.print the roots for both equations.

public class quadratic 
{
   public static void main (String[] args){
 
      int variable a = 1;
      int variable b = -7;
      int variable c = 10;
 
system.out.println(compute roots(equation);
}
 
public static int(compute roots(variable a, variable b, variable c); {
 
   int roots = variable -b + math.sqrt((variable b * variable b) - (4 * a * c)/(2*a));
 
     return root;
}
}

I know im missing the other equation for the root with subtracting the square root, and i dont know how to say my given equation im using, 0 = x2 -7x +10...in order to declare my ints. maybe you can help me where I went wrong?

You're java syntax is a bit off Also, it's not possible for a method to return 2 values, so I removed the helper method. Don't know if you have to handle imaginary roots, I left that out. I would also highly recommend using doubles when computing quadratic roots

public class Quadratic 
{
   public static void main (String[] args){
           double a = 1;
           double b = -7;
           double c = 10;
          // compute positive root
          double positive_root = (-b+Math.sqrt(b*b-4*a*c))/(2*a);
          // compute negative root
          double negative_root = (-b-Math.sqrt(b*b-4*a*c))/(2*a);          
          system.out.println(positive_root + "\n"+negative_root);
     }
}

... they are the coefficients to the quadratic equation. In other words, you (or the user) gets to choose them. I don't see much use in this program, it can only solve one quadratic equation

Unless your assignment specifically told you to find the solution to only one equation, I would make it so the user could input any values of a,b, and c, and also add support for imaginary roots.

actuallly i would prefer if it included methods and returned them this way...

can you look this one over and make any changes to fix it pleaseee

import java.util.*; //so that I can use Scanner
 
public class quadratic
{
   public static void main (String[] args)
   {
      Scanner in = new Scanner(System.in);
 
      System.out.print("Please type a quadratic equation, which you would like to find out the roots.");
 
           double quadratic = in.nextDouble();
           double variablea = in.nextDouble();
           double variableb = in.nextDouble();
           double variablec = in.nextDouble();
 
           // calling the method
           double quadraticanswer = quadratic1(variablea, variableb, variablec);
        }
        // compute positive root
          public static double quadratic1(double a, double b, double c) {
          double positiveroot = (-b+Math.sqrt(b*b-4*a*c))/(2*a);
          return positiveroot;
        }
 
          // compute negative root
          public static double quadratic2(double a, double b, double c) {
          double negativeroot = (-b-Math.sqrt(b*b-4*a*c))/(2*a);
          return negativeroot;
          }
}

I think you might run into a problem by naming a variable quadratic and the class quadratic... not positive on this. As a general rule, always name classes starting with upper case letters, and variables/methods starting with lower case letters (the one exception being constructors, they must have the same name as the class, so should start with an upper-case letter).

Use following code

Scanner keyb = new Scanner(in);
int a = keyb.nextInt();
int b = keyb.nextInt();
int c = keyb.nextInt();
double d = pow(b,2);
double f = sqrt(d-(4*a*c));
double g = (-b+f)/2;
double h = (-b-f)/2;
out.printf("The Roots are %1.2f,%1.2f\n",g,h);

This code works, trust me. It's even formattted.

To be honest, you need to follow a good naming convention as helloworld said...

public class _ {
 
	private static int _ = 6;
 
	public _(){
		String _ = "Hello";
		System.out.println(_ + this._);
	}
 
	public static void main(String[] args) {
		_ _ = new _();
		_._ = 60;
		System.out.println(_._);
		System.out.println(_._(_));
	}
 
	public String _(_ _){
		 return Integer.toString(_._);
	}
 
}

:O

public class Ø
{
     public Ø()
     {
          System.out.println("No!");
     }
}

You tried to take the square root of a negative number. NaN stands for "not a number", which technically isn't true. It's just not a real number, but there are imaginary roots.