Giải thích các bước giải:
Bài 2:
$\begin{split}a.A&=x^3-3x^2+4\\&=x^3+x^2-4x^2+4\\&=x^2(x+1)-4(x^2-1)\\&=x^2(x+1)-4(x+1)(x-1)\\&=(x+1)(x^2-4x+4)\\&=(x-1)(x-2)^2\end{split}$
$\begin{split}b.B&=x^2+y^2-x^2y^2+xy-x-y\\&=(x^2+2xy+y^2)-x^2y^2-(xy+x+y)\\&=(x+y)^2-(xy)^2-(xy+x+y)\\&=(x+y-xy)(x+y+xy)-(x+y+xy)\\&=(x+y+xy)(x+y-xy-1)\\&=(x+y+xy)(x-1)(1-y)\end{split}$