the equation :

good luck

sorry, it's not in N but in Z

there isn't any difference ^^

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- December 21st 2008, 11:52 PMguigui51250
the equation :

good luck

sorry, it's not in N but in Z

there isn't any difference ^^ - December 22nd 2008, 02:28 AMPaulRS
First, we obviously have the trivial solution

Now suppose there's another solution

If and are not multiples of 3 then a contradiction.

Again if**only**one of them ( x or z) is multiple of 3 we get a contradiction ( try it).

So both, and are multiples of 3. And thus is multiple of 9, so it must be that is multiple of 3. Now set ; ;

We get: (dividing by 9)

And it follows by infinite descent that there can be no other solution. - December 22nd 2008, 03:04 AMguigui51250
yes good, i post an other equation ^^