a) x3 - 6xy + 9xy2 = x(x2 - 6y + 9y2)
d) 20xy2 + 5xy3 = 5xy2(4 + y)
b) x2 + 2xy - 15y2 (mình sửa đề 1 chút cho hợp lí)
= x2 + 5xy - 3xy - 15y2
= x(x + 5y) - 3y(x + 5y)
= (x - 3y)(x + 5y)
e) x3 + 2x2 + x
= x(x2 + 2x +1)
= x(x + 1)2
c) x2 - x - 6
= x2 - 3x + 2x - 6
= x(x - 3) + 2(x - 3)
= (x + 2)(x - 3)