\(a,x^2-4x+xy-4y=\left(x^2+xy\right)-\left(4x-4y\right)\\ =x\left(x+y\right)-4\left(x+y\right)\\ =\left(x+y\right)\left(x-4\right)\)
a) \(x^2-4x+xy-4y\)
\(=\left(x^2-4x\right)+\left(xy-4y\right)\)
\(=x\left(x-4\right)+y\left(x-4\right)\)
\(=\left(x-4\right)\left(x-y\right)\)
b: MNPQ là hình bình hành
a: \(x^2-4x+xy-4y=x\left(x-4\right)+y\left(x-4\right)=\left(x-4\right)\left(x+y\right)\)