不定方程2(x+y)=xy+7的所有整數解為______.

不定方程2(x+y)=xy+7的所有整數解為______.

2x+2y=xy+7(2x-xy)+(2y-4)=3x(2-y)+2(y-2)=3(x-2)(2-y)=3∵x,y均為整數∴x-2,2-y也是整數∴(1)當x-2=1時,2-y=3解得:x=3,y=-1(2)當x-2=3時,2-y=1解得:x=5,y=1(3)當x-2=-1時,2-y=-3解得:x=1,y=5(4)當x-2=-3時,2-y=-1解得:x=-1,y=3故填:(3,-1)(5,1)(1,5)(-1,3)