(1,0 Đ) 9XY – 27XY2 = 9XY – 9XY.3Y (0,25) = 9XY(1-...

Câu 5: (1,0 đ) 9xy – 27xy

2

= 9xy – 9xy.3y (0,25) = 9xy(1-3y) (0,25) c) x

2

+2xy + y

2

– 64 = (x+y)

2

– 8

2

(0,25) = (x+y-8)(x+y+8) (0,25)