a) 3x² - 7x + 2
= 3x² - 6x - x + 2
= (3x² - 6x) - (x - 2)
= 3x(x - 2) - (x - 2)
= (x - 2)(3x - 1)
Vậy 3x² - 7x + 2 = (x - 2)(3x - 1)
b) a(x² + 1) - x(a² + 1)
= ax² + a - (a²x + x)
= ax² + a - a²x - x
= (ax² - a²x) + (a - x)
= ax(x - a) - (x - a)
= (x - a)(ax - 1)
Vậy a(x² + 1) - x(a² + 1) = (x - a)(ax - 1)