A) X2−6X+ = ⇔5 0 X2−5X− + = ⇔X 5 0 X X( −5) (− X−5)=0− = = 5 0 5X X⇔ − − = ⇔  − = ⇔ =( 5)( 1) 0 1 0 1X Y X X X⇔ ⇔ ⇔   B) 2+ =21 3 =23  =12 1  =11− = = − = − =   X Y Y X Y YVẬY HỆ ÑÃ CHO CÓ NGHIỆM ( ; )X Y LÀ (1;1)M X= + −

2)a) x

2

−6x+ = ⇔5 0 x

2

−5x− + = ⇔x 5 0 x x( −5) (− x−5)=0− = = 5 0 5x x⇔ − − = ⇔  − = ⇔ =( 5)( 1) 0 1 0 1x y x x x⇔ ⇔ ⇔   b) 2+ =213 =23=12 1=11− = = − = − =   x y y x y yVậy hệ ñã cho có nghiệm ( ; )x y(1;1)M x= + −