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## #1 2005-12-30 20:49:36

krassi_holmz
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### Solving diophantine equations

I need to make a program that solves different diophantine equations.
Can someone help me?

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## #2 2005-12-30 20:50:56

krassi_holmz
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### Re: Solving diophantine equations

1. ax+by=c

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## #3 2005-12-31 06:12:52

John E. Franklin
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### Re: Solving diophantine equations

#### Code:

```              ax + by = c
by = -ax + c
y = (-a/b)x + (c/b)

So y = at + ?1? and
x = bt + ?2?

-------
Put into original equation ax + by = c
a(bt + ?2?) + b(at + ?1?) = c
abt + a?2? + bat + b?1? = c
2bat + a?2? + b?1? = c
---------

y=7x + .3

y=7t + ?
x=t + ?
No integer solutions for this 7x + .3
---------
No luck yet.```

Imagine for a moment that even an earthworm may possess a love of self and a love of others.

## #4 2005-12-31 07:56:27

krassi_holmz
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### Re: Solving diophantine equations

For lineal d.e. we can use the this

Last edited by krassi_holmz (2006-01-01 07:10:13)

IPBLE:  Increasing Performance By Lowering Expectations.

## #5 2006-01-01 05:32:36

John E. Franklin
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### Re: Solving diophantine equations

At wolfram's site, equation # 6 has a  "+ 1"  in it (Euclidian thing).
I wonder why it always works out to a one, like the example they have?

Last edited by John E. Franklin (2006-01-01 05:33:03)

Imagine for a moment that even an earthworm may possess a love of self and a love of others.

## #6 2006-01-01 06:52:50

John E. Franklin
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### Re: Solving diophantine equations

Also equation # 10 at their site has an incorrect sign, I think.

Imagine for a moment that even an earthworm may possess a love of self and a love of others.

## #7 2006-01-01 08:28:42

John E. Franklin
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### Re: Solving diophantine equations

I found this a very useful page on this subject.

http://uzweb.uz.ac.zw/science/maths/zimaths/62/dioph.htm

or

Press this to go there.

My favorite part is at the end of the page:

#### the web page wrote:

(i)    The equation 3x + 6y = 22 has no solution since (3, 6) = 3 does not divide 22.

(ii)   The equation 7x + 11y = 13 has solution x = -39, y = 26. For

11 = 1·7 + 4,    7 = 1·4 + 3,    4 = 1·3 + 1.
Thus (7, 11) = 1, which divides 13. Further, working from the last equation back to the first,

1 = 4 - 3 = 4 -(7-4) = 2·4 - 7 = 2·11 - 3·7.
Hence

7·(-3) + 11(2) = 1,        7·(-39) + 11(26) = 13.
The other solutions are given by

x = -39 + 11r,        y = 26 - 7r
where r is any integer.

Last edited by John E. Franklin (2006-01-01 08:32:35)

Imagine for a moment that even an earthworm may possess a love of self and a love of others.

## #8 2006-01-01 22:12:53

krassi_holmz
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### Re: Solving diophantine equations

OK. We have simple alogritm for ax+by. I know it as Euler's reduction algoritm.
The next general case:
ax^2+by=c

IPBLE:  Increasing Performance By Lowering Expectations.