Consider the solution of quadratic equation x^2 + 4xy + y^2 = c. x, y are integers iff
3y^2 + c is a square. If c does not have factor 3, or is a square, it is impossible. Easy to find counterexample:
x = 13 (1, 2), y = 22 (1, 3) and x^2 + 4xy + y^2 = 286 has no interger solution.
Maybe I am wrong. An Counterexample.
所有跟帖:
• 回复:Maybe I am wrong. An Counterexample. -cma- ♂ (163 bytes) () 03/11/2012 postreply 13:04:23
• HI,X=19,Y=-1。 -jinjing- ♀ (0 bytes) () 03/11/2012 postreply 15:30:43