Chọn câu sai A. 15x^2 + 10xy = 5x(3x + 2y)

Ta có

+) 15x² + 10xy = 5x.3x + 5x.2y = 5x(3x + 2y)

+) 35x(y – 8) – 14y(8 – y) = 7.5x(y – 8) + 7.2y(y – 8)

= (7.5x + 7.2y)(y – 8) = 7(5x + 2y)(y – 8)

+) -x + 6x²y – 12xy + 2 = (6x²y – 12xy) – (x – 2)

= (6xy.x – 6xy.2) – (x – 2)

= 6xy(x – 2) – (x – 2)

= (6xy – 1)(x – 2)

+) x³ – x² + x – 1= x².x – x² + x – 1

= x²(x – 1) + (x – 1)

= (x² + 1)(x – 1)

Vậy A, B, D đúng, C sai

Đáp án cần chọn là: C