Solving Pell's Equation: I'm Stuck!

  • Context: Undergrad 
  • Thread starter Thread starter wii
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around solving the Pell-like equation x² - 18y² = 12, with a focus on finding integer solutions. Participants explore different approaches and clarify the nature of the solutions.

Discussion Character

  • Exploratory, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant suggests starting by finding √18 and determining the ratio x/y, but expresses confusion and halts progress.
  • Another participant notes that without specifying the set for x and y, the equation has an infinite number of solutions, proposing a parametric representation involving hyperbolic functions.
  • A later reply clarifies that both x and y must be integers, which may affect the nature of the solutions.
  • One participant asserts that there is no solution to the equation.

Areas of Agreement / Disagreement

The discussion contains competing views regarding the existence of solutions, with some participants suggesting the possibility of solutions under certain conditions, while at least one participant claims there is no solution.

Contextual Notes

The discussion does not resolve the assumptions regarding the nature of the solutions, particularly the requirement for x and y to be integers, and how this impacts the overall solvability of the equation.

wii
Messages
12
Reaction score
0
I want to solve this equation

x^2 - 18 y^2 = 12

Any suggestion?

I thought , we have to find \sqrt 18and then find x/y

BUT I was confused and then stopped solving
 
Physics news on Phys.org
This equation has 2 unknowns. If you don't specify what set x and y are elements of, for example integer, it has an infinite set of solutions that can be represented parametrically as:

<br /> \begin{array}{l}<br /> x = \pm 2 \sqrt{3} \, \cosh{t} \\<br /> <br /> y = \frac{2 \sqrt{3}}{3} \, \sinh{t}<br /> \end{array}<br />
 
Last edited:
Sorry,
Both x & y are integers.
 
You might get more help if you posted this in the Number Theory section...
 
There is no solution.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
11K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
Replies
1
Views
10K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 13 ·
Replies
13
Views
4K