Saturday, 21 December 2013

number theory - showing that the Diophantine 3x2+2=y2+6z3 equation has no solutions



I'd really love your help with showing that the Diophantine 3x2+2=y2+6z3 equation has no solutions.



I know that Diophantine equation of the form ax+by+cz=d iff gcd, but how do I deal with the squares?



Any hints? suggestions?



Thanks!



Answer



If (x,y,z) is a solution, then looking modulo 3 you should have
y^2\equiv2\pmod3



It is then easy to see that there is no integer satisfying this equation.


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