Đáp án:
a, 8x³ - y³ - 6xy(2x - y)
=[(2x)³ - y³] - 6xy(2x - y)
=(2x - y).[(2x)² + 2x.y + y²] - 6xy(2x - y)
=(2x-y).(4x² + 2xy +y²) - 6xy(2x - y)
=(2x - y).(4x² + 2xy + y² - 6xy )
=(2x - y).(4x² - 4xy + y²)
=(2x - y).(2x - y)²
=(2x - y)³
b, (3x + 2)² - 2(x - 1)(3x + 2) + (x - 1)²
=[3x + 2 - (x - 1)]²
= ( 3x + 2 - x + 1)²
= (2x + 3 )²