Tu de bai suy ra 2y+2x=xy<=>...<=>y(2-x)= -2x<=>y=2x/(x-2)<=>y=(2x-4+4)/(x-2)<=>y=2+4/(x-2)
vi x la so nguyen Dưỡng nen x-2 la so nguyen duong va la ước cua 4 => x-2 =1 hoặc x-2= 4 => x=3 hoac x=6
Voi x=3 => y= 6
voi x=6=> y=3
vay cac cap so nguyen duong (x;y) can tim la (3;6); (6;3)
.....
Sau khi chi ra x-2 la uoc nguyen duong cua 4
Co 3 Truong hop
x-2 =1; x-2=2;x-2=4
Tu do tinh duoc x=3;x=4;x=6. Suy ra cac gia tri tuong ung cua y
co 3 cap so nguyen duong x, y can Tim:(3;6);(4 ;4);(6;3)