1)
a) \(x^2+xy-x-y\)
\(=\left(x^2+xy\right)-\left(x+y\right)\)
\(=x.\left(x+y\right)-\left(x+y\right)\)
\(=\left(x+y\right).\left(x-1\right)\)
b) \(\left(x-y\right)^2-4\)
\(=\left(x-y\right)^2-2^2\)
\(=\left(x-y-2\right).\left(x-y+2\right)\)
Chúc bạn học tốt!