【5點】唔識計數....急!!!!

(a - b) - (a - b)^2
= (a - b)[1 - (a - b)]
= (a - b)(1 - a + b)

1 - a + a^2 - a^3
= (1 - a) + a^2(1 - a)
= (1 - a)(1 + a^2)

x^2 - 4x + 4
= (x)^2 - 2(x)(2) + (2)^2
= (x - 2)^2

2x^2 + 7x + 3
= (2x + 1)(x + 3)