Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.

Topic: Pell type equations
Replies: 29   Last Post: Apr 29, 2012 5:37 PM

 Messages: [ Previous | Next ]
 Terry M Posts: 15 Registered: 4/26/12
Re: Pell type equations
Posted: Apr 27, 2012 8:51 AM

Hi

"Helmut Richter" <hhr-m@web.de> wrote in message
> On Fri, 27 Apr 2012, Terry M wrote:
>

>> where x and y are coprime but can find no such solutions for 5x^2 + 45 =
>> y^2

>
> Without the restriction of coprimeness there are solutions, e.g. x=6, y=15
>
> With this restriction, there are none:
>
> A square is 0, 1, 4, or 7 (mod 9)
> Five times a square os 0, 5, 2, or 8 (mod 9)
>
> So the equation can only be fulfilled when both 5x^2 and y^2 are 0 (mod
> 9).
>

So I was making hard work of it, lol

Many thanks Helmut ;-)

> --
> Helmut Richter

Date Subject Author
4/26/12 Terry M
4/26/12 Dan Cass
4/26/12 Dan Cass
4/26/12 bert
4/26/12 Terry M
4/26/12 amzoti
4/26/12 Timothy Murphy
4/27/12 Terry M
4/27/12 Helmut Richter
4/27/12 Terry M
4/28/12 Helmut Richter
4/28/12 Terry M
4/28/12 Helmut Richter
4/28/12 Terry M
4/28/12 Terry M
4/28/12 Helmut Richter
4/28/12 Terry M
4/29/12 Terry M
4/29/12 Terry M
4/29/12 Helmut Richter
4/29/12 Terry M
4/29/12 Terry M
4/29/12 Terry M
4/28/12 Timothy Murphy
4/28/12 Terry M
4/28/12 Helmut Richter
4/28/12 Terry M
4/29/12 Timothy Murphy
4/29/12 Helmut Richter
4/29/12 Timothy Murphy