Finding roots of quadratic equation using a specific class

Question

i have this assignment that asks me to write a code that determines the roots of a quadratic equation (ax^2 + bx + c = 0). but i have to use the university's library (type.lib.Equation;).

i almost got everything figured out, except the case where there are two roots. i can get the 1st root but i'm still circling around to get the the 2nd root

my code so far

import java.util.Scanner;
import java.io.PrintStream;
import type.lib.Equation;

public class Check05A
{

    /**
     * @param args
     */
    public static void main(String[] args)
    {
        PrintStream output = System.out;
        Scanner input = new Scanner(System.in);

        output.println("Enter a,b,c pressing ENTER after each... ");
        double a = input.nextDouble();
        double b = input.nextDouble();
        double c = input.nextDouble();
        output.print("The equation: ");
        Equation x = new Equation(a, b, c);
        output.print(x);
        int root = x.getRootCount();




        if(root == 0)
        {
            output.println(" has no real roots.");
        }
        if(root == 1)
        {
            double r1 = x.getRoot(root);
            output.println(" has the single root: " + r1);
        }
        if(root == 2)
        {
            double r1 = x.getRoot(root);
            double r2 = -x.getRoot(root);
            output.println(" has the two roots: " + r2 + " and " + r1);
        }
        if(root == -1)
        {

            output.println("\nis an identity - any value is a root.");
        }









    }

}

for example 1, 2, -4 should output as :

"has the two roots: -3.23606797749979 and 1.2360679774997898"

Answer 1

You're just putting negative sign to root 1.

This isn't always the case.

Look up the formula for finding the roots for a quadratic equation:

x=\frac{-b \pm \sqrt {b^2-4ac}}{2a}.

and inside your function x.getRoot(), return two values inside an array.

Answer 2

*Please note that this answer is for only TI-84 calculators using If statements to find the roots of any nth degree polynomial. If this does not answer the question for you, please move on.

I made a TI-84 program that is helpful to find the roots of any nth degree polynomial. Here is the code:

(note that Z and S were set to be the derivatives of f and g; you have to find these yourself (I will update this code later with a parameter where it will get f' and g' by itself. Set z and s to 1 to use it to find GCF or roots!) (Also, Y1 is found in vars, if you tab right after clicking vars button, pressing enter, then enter again)

To start, put the function/s that you are working with into Y1, Y2, etc...

enter code here :Prompt F,G`:Prompt Z:Prompt S:If Y1=F:If Y2=G:F*G=FS+GZ->H :If X≥Y:X-Y=I->I:Disp I:If I=0:If I>0:Repeat X-Y=J->J:Disp J

That's it! Super simple, but so helpful! Let me know of any improvements (I am going to make a derivative finder program soon to embed into this code soon!)

Thanks so much, and have fun with the code! -Evan