若存在正整数n,使2n²+1,3n²+1,6n²+1都是完全平方数
则(2n²+1)(3n²+1)(6n²+1)是完全平方数
则36n²(2n²+1)(3n²+1)(6n²+1)
即36n^2(6n^2+1)(3n^2+1)(2n^2+1)
= 36n^2 (36n^6+36n^4+11n^2+1)
=36n^2 [9n^2(2n^2+1)^2+2n^2+1]
= (18n^2)^2(2n^2+1)^2+36n^2(2n^2+1)
=(36n^4+18n^2+1)^2-1是完全平方数
(36n^4+18n^2+1)^2是完全平方数
(36n^4+18n^2+1)^2-1不可能是完全平方数