2x2+5y2+2xy−8x−22y+22<0
=> 4x2+10y2+4xy−16x−44y+44<0
=> (2x+y−4)2+9(y−2)2<8
Vì {8≥(2x+y−4)2≥08≥9(y−2)2≥0
=> 9(y−2)2=0=>y=2 (x,y nguyên)
=> (2x−2)2≤8
=> Tự giải x
2x2+5y2+2xy−8x−22y+22<0
=> 4x2+10y2+4xy−8x−44y+44<0
=> (2x+y−4)2+9(y−2)2<8
Vì {8≥(2x+y−4)2≥08≥9(y−2)2≥0
=> 9(y−2)2=0=>y=2 (x,y nguyên)
=> (2x−2)2≤8
=> Tự giải x