An algebra problem....

kinkon

Well-known member
  • Aug 5, 2007
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    Kandy ♕ පතිරූප දේස වාසෝ
    Morning Monday GIF
     

    EKGuest

    Well-known member
  • Nov 16, 2022
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    For those who are interested....

    Find the whole number solutions for the following equation.

    View attachment 150893

    I couldn't solve this problem but we can write code to find some of the answers for x and y.

    C#:
    using System;
    
    internal class Program
    {
        static void Main(string[] args)
        {
            long rangeMax = 10000;
            long rangeMin = -rangeMax;
    
            for (long x = rangeMin; x <= rangeMax; x++)
            {
                for (long y = rangeMin; y <= rangeMax; y++)
                {
                    if (  (x * x) + (4 * y * y) == ( (x * y - 14) * (x * y - 14) )  )
                    {
                        Console.WriteLine("x = {0}\ty={1}", x, y);
                    }
                }
            }
    
            Console.ReadLine();
        }
    }

    1.png


    Note that above output doesn't prove those are the only answers for x and y. It simply shows the answers for x and y within the seleted range, (-10,000 to 10,000)
     

    imhotep

    Well-known member
  • Mar 29, 2017
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    I couldn't solve this problem but we can write code to find some of the answers for x and y.

    C#:
    using System;
    
    internal class Program
    {
        static void Main(string[] args)
        {
            long rangeMax = 10000;
            long rangeMin = -rangeMax;
    
            for (long x = rangeMin; x <= rangeMax; x++)
            {
                for (long y = rangeMin; y <= rangeMax; y++)
                {
                    if (  (x * x) + (4 * y * y) == ( (x * y - 14) * (x * y - 14) )  )
                    {
                        Console.WriteLine("x = {0}\ty={1}", x, y);
                    }
                }
            }
    
            Console.ReadLine();
        }
    }

    View attachment 192441

    Note that above output doesn't prove those are the only answers for x and y. It simply shows the answers for x and y within the seleted range, (-10,000 to 10,000)
    Good effort.. (y) Thanks...!!!
    It's over an year since I posted it and I forgot to post the solution as well. Yes... these two are the Integer solutions to the problem, other than the trivial integer solution x=0, y = ± 7 and y=0, x = ± 14

    By rearranging it you can solve it algebraically for a generalized solution

    y = (14x - SQR(x^4 - 4x^2 + 784))/ (x^2 - 4) when X^2 is not equal to 4
    y= ((SQR(x^4 - 4x^2 + 784) + 14x))/(x^2 - 4) when x^2 is not equal to 4

    When x^2 is equal to 4 then.
    when x = 2 , y = 24/7 also when x = -2 , y = -24/7
     
    Last edited:

    07sanjeewakaru

    Well-known member
  • Feb 9, 2013
    5,527
    1,809
    113
    ලංකාවෙ අඩා...!
    I couldn't solve this problem but we can write code to find some of the answers for x and y.

    C#:
    using System;
    
    internal class Program
    {
        static void Main(string[] args)
        {
            long rangeMax = 10000;
            long rangeMin = -rangeMax;
    
            for (long x = rangeMin; x <= rangeMax; x++)
            {
                for (long y = rangeMin; y <= rangeMax; y++)
                {
                    if (  (x * x) + (4 * y * y) == ( (x * y - 14) * (x * y - 14) )  )
                    {
                        Console.WriteLine("x = {0}\ty={1}", x, y);
                    }
                }
            }
    
            Console.ReadLine();
        }
    }

    View attachment 192441

    Note that above output doesn't prove those are the only answers for x and y. It simply shows the answers for x and y within the seleted range, (-10,000 to 10,000)
    These are the only solutions......
    ek.JPG


    ek2.JPG

    erk3.JPG

    ------ Post added on Dec 23, 2022 at 2:53 PM
     
    Last edited: